Basics of C Programming UNITI Basic Terminologies Computers

Basics of C Programming UNIT-I

Basic Terminologies • Computers -really dumb machines because they do only what we are told to do. • A computer program - is just a collection of the instructions necessary to solve a specific problem. • Algorithm-The approach or method that is used to solve the problem.

Continue. . For example: Develop a program that tests if a number is odd or even. • First express the solution to the problem in terms of an algorithm • Then develop a program that implements that algorithm. Algorithm for above problem 1. First, divide the number by two. 2. If the remainder of the division is zero, the number is even; 3. Otherwise, the number is odd.

1. Machine Level Language - Binary numbers that corresponded directly to specific machine instructions and locations in the computer’s memory. 2. Low-Level Language (Assembly language) - permits the programmer to use symbolic names to perform various operations and to refer to specific memory locations. Assembler - A special program that translates the assembly language program from its symbolic format into the specific machine instructions of the computer system

Disadvantage of Assembly language • Machine dependent -Different processor types have different instruction sets. Assembly language program will not run on a different processor type without being rewritten. • Not Portable - Programmer learn the instruction set of the particular computer system to write a program in assembly language.

3. Higher-level languages (HLL)-came to overcome the machine dependent issue of low-level language. • FORTRAN (FORmula TRANslation) was the first higher-level language. • Merits: Machine independent - A program could be written in any language is to be run on any machine that supported the language with few or no changes.

Compiler • To support HLL, a special computer program is used to translates the statements of the HLL into particular instructions of the computer. • First, Analyzes a program which written in a particular computer language (HLL) • Then translates it into a form that is suitable for execution on particular computer system.

Operating system - A program that controls the entire operation of a computer system. • All I/O operations that are performed on a computer system are channelled through the operating system. • Also manage the computer system’s resources. • Handle the execution of programs. • Most popular operating systems today is the Unix, Microsoft Windows XP.

Compilation Process 1. Write Source Program using Text Editor • The program that is to be compiled is first typed into a file on the computer system. • A text editor is usually used to enter the C program into a file. • C programs can typically be given any name provided the last two characters are “. c”. • For example, vi is a popular text editor used on Unix systems. The program that is entered into the file is known as the source program because it represents the original form of the program expressed in the C language.

2. Debugging Phase: Compiler checks each program statement in source program to conforms the syntax and semantics of the language. *unbalanced parentheses (syntactic error) * variable that is not “declared” (semantic error) • If any mistakes are discovered then it reported to the user and the compilation process ends right there. • So errors have to be corrected in the source program (with the use of an editor), and the compilation process must be restarted.

Creation of Object code file • Once all syntactic and semantic errors have been removed from the program, the compiler then proceeds to take each statement of the program and translate it into a “lower” form. (translated into the equivalent statements in assembly language) • Next the assembler takes each assembly language statement and converts it into a binary format known as object code, which is then written into another file on the system. • This file typically has the same name as the source file with the last letter an “o” (in unix) or “obj” (in windows) instead of a “c”.

3. Linking Process (Creation of executable object code) • Now object code is ready to be linked. If the program uses other programs that were previously processed by the compiler, then those programs are linked together. • Programs that are used from the system’s program library are also searched and linked together with the object program during this phase. • The process of compiling and linking a program is often called building. • The final linked file is an executable object code which is ready to be run or executed. It is stored in another file on the system, (In Unix, this file is called “a. out”, In Windows, same name as the source file, with “exe” extension).

4. Loading & Execution • To run the program, an executable object code file must be loaded into the computer’s memory and initiating its execution. • When the program is executed, each of the statements of the program is sequentially executed in turn. • If the program requests any data from the user, known as input, the program temporarily suspends its execution so that the input can be entered. Or, the program might simply wait for an event, such as a mouse being clicked, to occur. • Results that are displayed by the program, known as output, appear in a window called the console. Or, the output might be directly written to a file on the system.

• If all goes well, the program performs its intended functions. • If the program does not produce the desired results, it is necessary to go back and reanalyze the program’s logic. This is known as the debugging phase, during which an attempt is made to remove all the known bugs from the program. • To do this, make changes to the original source program. So the entire process of compiling, linking, and executing the program must be repeated until the desired results are obtained.

Compiler Vs Language Interpreters • Another method used for analyzing and executing programs developed in a higher-level language. • Source Programs are not compiled but are interpreted. • An interpreter analyzes and executes the statements of a program at the same time. This method usually allows programs to be more easily debugged. • It is slower than compilation because statements are not converted into their lowest-level form in advance of their execution. Example • BASIC and Java are two programming languages in which programs are often interpreted and not compiled. • Other examples include the Unix system’s shell and Python. • Some vendors also offer interpreters for the C programming language.

Integrated Development Environment • The process of editing, compiling, running, and debugging programs is managed by a single integrated application known as an IDE. • An IDE is a windows-based program that allows you to easily manage large software programs, edit files in windows, and compile, link, run, and debug your programs. • Most IDEs also support program development in several different programming languages in addition to C, such as C# and C++. Example • In Mac OS X, Code. Warrior and Xcode are two IDEs used. • In Windows, Microsoft Visual Studio is a popular IDE. • Kylix is a popular IDE for developing applications under Linux.

Programming paradigms • Way to classify programming languages based on their features. • Languages can be classified into multiple paradigms. • Some paradigms are concerned mainly with implications for the execution model of the language, • Other paradigms are concerned mainly with the way that code is organized. • Yet others are concerned mainly with the style of syntax and grammar.

Execution model & Side effects Ø Execution model specifies how work takes place. – Every programming language has an execution model cover What is an indivisible unit of work? & What are the constraints on the order in which those units of work take place? – This order may be chosen ahead of time, or it can be dynamically determined as the execution proceeds. – The implementation of an execution model can be via compiler/ interpreter, and includes a runtime system. Ø Side effects -way that a program interacts with the outside world (people, file systems, other computers on networks). But the degree to which side effects are used depends on the programming paradigm.

Example: C programming language has a concept called a statement. Statements are indivisible units of work and that they proceed in the same order as their syntactic appearance in the code (except when a control statement such as IF or WHILE modifies the order). The C language actually has an additional level to its execution model, which is the order of precedence. It states the rules for the order of operations within a single statement.

Common programming paradigms • Imperative which allows side effects. (in which the programmer instructs the machine how to change its state) o Object-oriented which groups instructions together with the part of the state they operate on. o Procedural which groups instructions into procedures. • Declarative in which the programmer merely declares properties of the desired result, but not how to compute it. – Functional in which the desired result is declared as the value of a series of function applications. – Logic in which the desired result is declared as the answer to a question about a system of facts and rules. – Mathematical in which the desired result is declared as the solution of an optimization problem

• Imperative paradigm has two main features: they state the order in which operations occur and they allow side effects. Most objectoriented languages are also imperative languages. • Declarative paradigm does not state the order in which to execute operations. Instead, they supply a number of operations that are available in the system, along with the conditions under which each is allowed to execute. The execution model tracks which operations are free to execute and chooses the order on its own.

Languages support single/multiple paradigms • Languages are designed to support one paradigm (Smalltalk supports object-oriented programming, Haskell supports functional programming). • Multi paradigm supported languages can be purely procedural, purely object-oriented, or can contain elements of both or other paradigms. • Example: Object Pascal, C++, Java, C#, Scala, Visual Basic, Lisp, Scheme, Perl, PHP, Python, Ruby, Oz, and F# • Software designers and programmers decide how to use those paradigm elements.

Introduction to C • C is a high-level structured oriented programming language used in general purpose programming, developed by Dennis Ritchie at AT&T Bell labs, USA between 1969 and 1973. • Some Facts about C Programming Language • In 1988, the American National Standards Institute (ANSI) has formalized the C language. • C was invented to write UNIX operating system. • C is a successor of ‘Basic Combined Programming Language’ (BCPL) called B language. • Linux OS, PHP and My. SQL is written in C. • C has been written in assembly language.

Uses of C Programming Language • In the beginning C was used for developing system applications e. g. : Database Systems, Language Interpreters, Compilers and Assemblers, Operating Systems, Network Drivers, Word Processors C has Become Very Popular for Various Reasons • One of the early programming languages. • Still the best programming language to learn quickly. • C language is reliable, simple and easy to use. • C language is a structured language. • Modern programming concepts are based on C. • It can be compiled on a variety of computer platforms. • Universities preferred to add C programming in their courseware.

Features of C Programming Language • C is a robust language with rich set of built-in functions and operators. • Programs written in C are efficient and fast. • C is highly portable, programs once written in C can be run on another machines with minor or no modification. • C is basically a collection of C library functions; we can also create our own function and add it to the C library. • C is easily extensible.

Advantages of C • C is the building block for many other programming languages. • Programs written in C are highly portable. • Several standard functions are there (like in-built) that can be used to develop programs. • C programs are basically collections of C library functions, and it’s also easy to add own functions in to the C library. • The modular structure makes code debugging, maintenance and testing easier. Disadvantages of C • C does not provide Object Oriented Programming (OOP) concepts. • There is no concept of Namespace in C. • C does not provide binding or wrapping up of data in a single unit. • C does not provide Constructor and Destructor.

1. Documentation Section - This is a comment block, which is ignored by the compiler. Comment can used anywhere in program to add info about program or code block, which will be helpful for developers to easily understand the existing code in the future. e. g. /* */, // 2. Link Section -This Section is the core part of the program in which compiler links the inbuilt function from the system library. e. g. # include < > 3. Definition Section -In this part, we define a symbolic constant. e. g. define PI = 3. 14 4. Global Declaration -When programmer wants to use some variables that are used in more than one function. The global declaration section is used to define those variables that are used globally within the entire program and is used in more than one function.

5. Main( ) -The main() is the main function where program execution begins. Every C program must contain only one main function. This section contains two parts. -These two parts are declared within the opening and closing curly braces of the main(). The execution of program begins at the opening brace ‘{‘ and ends with the closing brace ‘}’. -Also it has to be noted that all the statements of these two parts needs to be terminated with semi-colon. Declaration parts in which all variables and user defined functions are declared. Execution part in which program logic and other process is done. Two curly brackets “{…}” are used to group all statements together Or shows how much the main() function has its scope. 6. Subprogram Section -The sub-program section deals with all user defined functions that are called from the main(). These user defined functions are declared and defined usually after the main() function.

Compile & Run the first C program #include <stdio. h> void main () { printf ("Programming is fun. n"); } Note: to display multi line output printf ("Testing. . . n. . 1n. . . 2n. . 3n");

#include<stdio. h> #include<conio. h> void main() { int sum; clrscr(); sum = 50 + 25; printf ("The sum of 50 and 25 is %in", sum); getch(); }

C Tokens Ø The smallest element in the C language is the token. Ø It may be a single character or a sequence of characters. C Tokens Identifiers Keywords Constants Strings operators Eg: main, avg Eg: int, for Eg: 17, 15. 5 Eg: “ab” Eg: + - sp. I symbol Eg: # $ %

Identifiers Ø Identifiers are names given to various program elements such as variables, functions and arrays etc, . Ø Eg: #define N 10 #define a 15 int xval; void sum_of_num( )

The rules forming identifier Ø First character must be alphabetic or underscore. Ø Must consist only of alphabetic characters, digits, or underscores. Ø Only the first 31 characters of an identifier are significant and are recognized by the compiler. Ø Cannot use a keywords or reserved word (e. g. main, include, printf & scanf etc. ). Ø No space are allowed between the identifiers etc, . Ø C is case sensitive, e. g. My_name my_name.

Working with Variables • Assign symbolic names for storing program computations and results in memory known as variable names. • A variable name can be chosen by you. • The C language allows storing different types of data into the variables & proper declaration for the variable is made before it is used in the program. • Variables can be used to store floating-point numbers, characters, and even pointers to memory locations.

Suggestions on choosing variable name • Pick names that reflect the intended use of the variable (i. e. type of value or purpose). The reasons are obvious. • Just as with the comment statement, meaningful variable names can dramatically increase the readability of a program and pay off in the debug and documentation phases. • In fact, the documentation task is greatly reduced because the program is more selfexplanatory.

List of valid variable names Sum sum piece. Flag i J 5 x 7 Number_of_moves _sysflag List of not valid variable names with reason sum$value $ is not a valid character. piece flag Embedded spaces are not permitted. 3 Spencer Variable cannot start with a number int is a reserved word/name.

Keywords auto double int struct break else long switch case enum static register typedef char extern return union const float short unsigned while continue for signed void default goto sizeof do if

Constants • Any number, single character, or character string is known as a constant. • For example, the number 58 represents a constant integer value. • The character string "Programming in C" is an example of a constant character string. • C constant is just the written version of a number. For example 1, 0, 5. 73, 12. 5 e 9. We can specify our constants in octal or hexadecimal, or force them to be treated as long integers.

Constants Numeric Constants Integer Constant Real Constant Character Constants Single Character Constant String Constant

Numeric constants Integer constants Ø It is formed using a sequence of digits. ØDecimal - 0 to 9, ØOctal - 0 to 7. ØHexa - 0 to 9, A to F Real constants Ø It is formed using a sequence of digits but it contain decimal point. Ø length, height, price distance measured in real number Eg: 2. 5, 5. 11, etc.

Rules for defining Integer Constant Ø It must have atleast one digit. Ø Decimal point are not allowed. Ø No blank space or commas are allowed. Ø It can be either positive or negative. • Octal constants are written with a leading zero - 015. • Hexadecimal constants are written with a leading 0 x - 0 x 1 ae. • Long constants are written with a trailing L - 890 L.

Character constants Single character constant ØA character constant is a single character they also represented with single digit or a single special symbol which is enclosed in single quotes. Ø Eg: ‘a’, ‘ 8’, ’_’etc. String constants Ø String constant are sequence of characters enclosed with in double quote. Ø Eg: “Hello” , ” 444”, ”a” etc, .

• Character constants are written with in single quotes 'a', 'b', 'c'. • String constants are written with in double quotes “hello” • Character constants are rarely used, since string constants are more convenient. • A string constant is surrounded by double quotes e. g. "Brian and Dennis". The string is actually stored as an array of characters. The null character '' is automatically placed at the end of such a string to act as a string terminator. • Constant is a special types of variable which cannot be changed at the time of execution. Syntax: const int a=20;

Data Type • The C programming language provides five basic data types: int, float, double, char, and _Bool. • A variable declared to be of type int can be used to contain integral values only—that is, values that do not contain decimal places. • A variable declared to be of type float can be used for storing floating-point numbers (values containing decimal places). • The double type is the same as type float, only with roughly twice the precision. • The char data type can be used to store a single character, such as the letter a, the digit character 6, or a semicolon etc. • Finally, the _Bool data type can be used to store just the values 0 or 1. Variables of this type are used for indicating an on/off, yes/no, or true/false situation.

Variable Storage Sizes and Ranges • The amount of storage that is allocated to store a particular type of data. • It is not defined in the language. It is machinedependent. • You should never write programs that make any assumptions about the size of your data types. • Guaranteed that a minimum amount of storage will be set aside for each basic data type.

Data types Data type Size(bytes) Range -128 to 127 Format string char 1 %c int 2 -32, 768 to 32, 767 %d %i float 4 3. 4 e-38 to 3. 4 e+38 %f double 8 1. 7 e-308 to 1. 7 e+308 %lf

Octal & Hexadecimal notation – To express the octal constant 0177 represents the decimal value 127 (1 × 64 + 7 × 8 + 7) leading 0 used. – An integer can be displayed in octal notation by using format characters %o, the value is displayed in octal without a leading zero. – The format characters %#o does cause a leading zero to be displayed before an octal value. – Hexa representation Eg: int rgb. Color = 0 x. FFEF 0 D; – The format characters %x display a value in hexadecimal format without the leading 0 x, and using lowercase letters a–f for hexadecimal digits. – To display the value with the leading 0 x, you use the format characters %#x

The Floating Number Type float • Floating-point constants can also be expressed in scientific notation. The value 1. 7 e 4 is represents the value 1. 7 × 104. • The value before the letter e is known as the mantissa, whereas the value that follows is called the exponent. Letter e can be written in either lowercase or uppercase. • In the constant 2. 25 e– 3, the 2. 25 is the value of the mantissa and – 3 is the value of the exponent. • This constant represents the value 2. 25 × 10– 3, or 0. 00225.

• To display a value in scientific notation %e • %g can be used to let printf decide whether to display the floating-point value in normal floating-point notation or in scientific notation. This decision is based on the value of the exponent: If it’s less than – 4 or greater than 5, %e (scientific notation) format is used; otherwise, %f format is used.

The Boolean Data Type _Bool • A bool variable is defined to store just the values 0 and 1 that need to indicate a Boolean condition. For example, a variable of this type might be used to indicate whether all data has been read from a file. • By convention, 0 is used to indicate a false value, and 1 indicates a true value. • When assigning a value to a bool variable, a value of 0 is stored as 0 inside the variable, whereas any nonzero value is stored as 1. • To make it easier to work with bool variables in program, the standard header file <stdbool. h> defines the values bool, true, and false.

Data type Entire Data types in c Size(bytes) Range Format string Char 1 128 to 127 %c Unsigned char 1 0 to 255 %c Short or int 2 -32, 768 to 32, 767 Unsigned int 2 0 to 65535 Long 4 Unsigned long 4 0 to 4294967295 Float 4 3. 4 e-38 to 3. 4 e+38 Double 8 1. 7 e-308 to 1. 7 e+308 %lf Long Double 10 3. 4 e-4932 to 1. 1 e+4932 %lf -2147483648 to 2147483647 %i or %d %u %ld %lu %f or %g

Using the Basic Data Types #include <stdio. h> int main (void) { integer. Var = 100; floating. Var = 331. 79; double. Var = 8. 44 e+11; char. Var = 'W'; bool. Var = 3; printf ("integer. Var = %in", integer. Var); printf ("floating. Var = %fn", floating. Var); printf ("double. Var = %en", double. Var); printf ("double. Var = %gn", double. Var); printf ("char. Var = %cn", char. Var); printf ("bool. Var = %in", bool. Var); return 0; }

Output integer. Var = 100 floating. Var = 331. 790009 double. Var = 8. 440000 e+11 double. Var = 8. 44 e+11 char. Var = W bool. Var = 1;

Specifier Meaning %c – Print a character %d – Print a Integer %i – Print a Integer %e – Print float value in exponential form. %f – Print float value %g – Print using %e or %f whichever is smaller %o – Print actual value %s – Print a string %x – Print hexadecimal integer (Unsigned) lower case a – F %X – Print hexadecimal integer (Unsigned) upper case A – F %a – Print a unsigned integer. %p – Print a pointer value %hx – hex short %lo – octal long %ld – long unsigned integer.

Storage Classes • A storage class defines the scope (visibility) and life-time of variables and functions within a C Program. • Storage classes are auto, static, extern, and register. • A storage class can be omitted in a declaration and a default storage class is assigned automatically.

auto • This is the default storage class for all the variables declared inside a function or a block • Auto variables can be only accessed within the block/function they have been declared and not outside them. extern • Extern storage class simply tells us that the variable is defined elsewhere and not within the same block where it is used. • Basically, the value is assigned to it in a different block and this can be overwritten/changed in a different block as well. • An extern variable is nothing but a global variable initialized with a legal value.

static • Static variables have a property of preserving their value even after they are out of their scope! • They are initialized only once and exist till the termination of the program. By default, they are assigned the value 0 by the compiler. • No new memory is allocated because they are not re-declared. • Their scope is local to the function to which they were defined. • Global static variables can be accessed anywhere in the program. register • Have the same functionality as that of the auto variables. The only difference is that the compiler tries to store these variables in the register of the microprocessor if a free register is available. • Register variables to be much faster than variables stored in memory • But, we cannot obtain the address of a register variable using pointers.

If Storage Class is And can Variable Then it can be is be referenced initialized declared with auto Inside a BLOCK Within the BLOCK register Inside a BLOCK Within the BLOCK Comments Variable is initialized each time Any valid the BLOCK is expression entered; No default value. Assignment to register not guaranteed; Varying restrictions on types of variables that Any valid can be declared; expression Cannot take the address of a register variable; Initialized each time BLOCK is entered; No default value.

If Storage Class is And Variable Then it can be And can be is declared referenced initialized with static Outside any BLOCK Inside a BLOCK Anywhere within the file Within the BLOCK extern Outside any BLOCK Inside a BLOCK Anywhere within the file Within the BLOCK Comments Variables are initialized only once at the start of program Constant execution; expression only Values are retained through BLOCKs; Default value is 0. Variable must be declared in at least one place without the Constant extern keyword, or in expression only one place using the keyword extern and assigned an initial value.

If Storage Class is And Variable Then it can be is declared referenced Outside Omitted any (or) Not BLOCK specified Inside a BLOCK And can be initialized with Comments This declaration Anywhere can appear in within the only one place; file or by Constant Variable is other files expression initialized at that contain s only the start of appropriate program declaration execution; s Default value is 0. (See auto) Defaults to auto.

• The static storage class instructs the compiler to keep a local variable in existence during the life-time of the program. • Making local variables static allows them to maintain their values between function calls. #include <stdio. h> void func(void); /* function declaration */ static int count = 5; /* global variable */ main() { while(count--) { func(); } return 0; } void func( void ) { static int i = 5; /* local static variable */ i++; printf("i is %d and count is %dn", i, count); }

Operators in C • An operator is a symbol used to do a mathematical or logical manipulations. 1. Arithmetic operators 2. Relational Operators 3. Logical Operators 4. Assignment Operators 5. Increments and Decrement Operators 6. Conditional Operators 7. Bitwise Operators 8. Special Operators

Arithmetic Operators Operator Meaning + Addition or Unary Plus – Subtraction or Unary Minus * Multiplication / Division % Modulus Operator

Arithmetic Operations • Integer Arithmetic Let x = 27 and y = 5 x + y = 32 x – y = 22 x * y = 115 x % y = 2 x / y = 5 • Floating point Arithmetic Let x = 14. 0 and y = 4. 0 then x + y = 18. 0 x – y = 10. 0 x * y = 56. 0 • Mixed mode Arithmetic 15/10. 0 = 1. 5

Sample program #include<stdio. h> // Header File #include <conio. h> int b=10; //Global Declaration void main ( ) /* main is the starting of every c program */ { int a, c; //Local Declaration clrscr( ); scanf(“%d”, &a); printf(“ n The sum of the two values: ”); c = a+b; printf(“%d”, c); getch( ); }

Division operator on Different Data Type Operation Result Example int/int 5/2 int/real 5/2. 0 = 2. 5 real/int real 5. 0/2 = 2. 5 real/real 5. 0/2. 0 = 2. 5 = 2

Sample program #include<stdio. h> #include <conio. h> void main ( ) { int a=10, b=4, c; float d=3, e; clrscr( ); c = a/b; printf(" n value a/b is: %d", c); e = a/d; printf("n value a/d is: %f", e); getch( ); }

Output value a/b is: 2 value a/d is: 3. 333333

Relational Operators Ø It is used to compare two or more operands. Ø 5 < 9 which will return 1 Operator < <= > >= == Meaning is less than or equal to is greater than or equal to is equal to

Logical Operators Ø It is used to combine the result of two or more condition. Ø Eg: (i>10)&&(j>5). Ø (i>10)||(j>5) etc, . Operator Meaning && Logical AND || Logical OR ! Logical NOT

Sample program #include<stdio. h> #include <conio. h> void main ( ) { int a=10, b=3, c=5, e; clrscr( ); if(a>b) // relational operator { printf(" n a is bigger than b"); } if((a>b)&&(a>c)) //Logical operator { printf(" n a is biggest"); } getch( ); }

Output a is bigger than b a is biggest

Assignment Operators It is used to assign a value or expression etc to a variable. Compound operator It is also used to assign a value to a variable. Eg: x + = y means x = x + y Nested operator It is used for multiple assignment. Eg: i = j = k = 0; Statement with simple assignment operator Statement with shorthand operator a=a+1 a=a– 1 a = a * (n+1) a = a / (n+1) a=a%b a += 1 a -= 1 a *= (n+1) a /= (n+1) a %= b

Increment and Decrement Operators 1. ++ variable name (Pre Increment) 2. variable name++ (Post Increment) 3. – –variable name (Pre Decrement) 4. variable name– – (Post Decrement) Consider the following m = 5; y = ++m; (prefix) value of y and m would be 6 m = 5; y = m++; (post fix) value of y will be 5 and that of m will be 6.

Sample Program #include<stdio. h> #include <conio. h> void main ( ) { int a=5; clrscr( ); printf(" n Post increment Value: %d", a++); printf(" n Pre increment Value: %d", ++a); printf(" n Pre decrement Value: %d", --a); printf(" n Post decrement Value: %d", a--); getch( ); }

Output Post increment Value: 5 Pre increment Value: 7 Pre decrement Value: 6 Post decrement Value: 6

Conditional or Ternary Operator It is used to checks the condition and execute the statement depending on the condition. The conditional operator consists of 2 symbols the question mark (? ) and the colon (: ) syntax: exp 1 ? exp 2 : exp 3 a = 10; b = 15; x = (a > b) ? a : b

Sample Program #include<stdio. h> #include <conio. h> void main ( ) { int a=5, b=8, c; clrscr( ); c = a>b? a: b; //Conditional operator printf(" n The Larger Value is%d", c); getch( ); } Output: The Larger Value is 8

Bitwise Operators Ø It is used to manipulate data at bit level. Ø Eg: a=5 i. e 0000 0101 b=4 i. e 0000 0100 Then a & b = 0000 0100 a | b = 0000 0101 etc, . Operator Meaning & Bitwise AND | Bitwise OR ^ Bitwise Exclusive << Shift left >> Shift right

Sample program #include<stdio. h> #include <conio. h> void main ( ) { int a=5, b=4, c; //char a=5, b=4, c; clrscr( ); c = a&b; printf(" n value a&b is: %d", c); getch( ); } Output: value a&b is: 4

Special Operator Ø comma operator ( , ) Ø sizeof operator Ø pointer operator (& and *) Ø member selection operators (. and ->). The Comma Operator -to link related expressions together. Eg: int x=5, y=10;

Contd…sizeof #include<stdio. h> #include <conio. h> void main ( ) { int c; clrscr( ); printf(" n size of int is: %d", sizeof(c)); getch( ); } Output: size of int is: 2

Expression Ø An expression represent data item such as variable, constant are interconnected using operators. Ø Eg: Expression C Expression a+b+c a 2+b 2 a*a + b*b

Operator Precedence & Associativity Ø The arithmetic expressions evaluation are carried out based on the precedence and associativity. Ø The evaluation are carried in two phases. ØFirst Phase: High Priority operators are evaluated. ØSecond Phase: Low Priority operators are evaluated.

Contd… Precedence Operator High *, /, % Low +, -

Operator Precedence Chart Operator Type Operator Primary Expression Operators () []. -> expr++ expr-Unary Operators Associatively left-to-right * & + - ! ~ ++expr --expr (typecast) right-to-left sizeof() * / % + >> << < > <= >= Binary Operators == != & left-to-right ^ | && || Ternary Operator ? : right-to-left Assignment Operators = += -= *= /= %= >>= <<= &= ^= |= right-to-left Comma , left-to-right

Implicit type conversion • C allows mixing of constants and variables of different types in an expression. • C automatically converts intermediate values to the proper type so that the expression can be evaluated without loosing any significance. • Adheres to very strict rules and type conversion. • If operands are of different types then lower type is automatically converted to higher type before the operation proceeds. • The result is of higher type.

Explicit Conversion • We want to force a type conversion that is different from automatic conversion. int female_students=30, male_students=50; Radio=female_students / male_students; Above gives wrong result Ratio = (float) female_students / male_students Ø Type Conversion: Converting the type of an expression from one type to another type. Ø Eg: x = (int)10. 45

Sample Program #include<stdio. h> #include <conio. h> void main ( ) { int a=30, b=50; float c; clrscr( ); c=(float)a/b; printf("n. Output is: %f", c); getch( ); } OUTPUT Output is: 0. 6

Character Test Function Ø Ø Ø Ø It is used to test the character taken from the input. isalpha(ch) isdigit(ch) islower(ch) isupper(ch) tolower(ch) toupper(ch) etc, .

Decision Making Ø It is used to change the execution order of the program based on condition. Ø Categories: ØSelection structure (or) conditional branching statements ØLooping structure (or) Iterative statements Øbreak, continue & goto statements

Decision Making (cont) Sequential structure ØIn which instructions are executed in sequence. Selection structure ØIn which instruction are executed once based on the result of condition. Iteration structure ØIn which instruction are executed repeatedly based on the result of condition.

Conditional Branching Ø It allows the program to make a choice from alternative paths. Ø C provide the following selection structures Øif statement Øif - else statement Øif-else if statement ØNested if-else statement Øswitch-case

if Statement Syntax if (condition is true) { Statements; } True Statements Example: 1 (if) if (a>b) { printf (“a is larger than b”); } If condition False

Example #include<stdio. h> Output #include <conio. h> void main ( ) Enter the number: 12 { a is greater than 10 int a; clrscr( ); printf("n. Enter the number: "); scanf("%d", &a); if(a>10) { printf(" n a is greater than 10"); } getch( ); }

Syntax if (condition) { True statements; } else { False statements; } if…else Statement Example: 2 (if-else) if(n > 0) average = sum / n; else { } True statements printf("can't compute averagen"); average = 0; If Condition False statements

#include<stdio. h> #include <conio. h> void main ( ) { int a; clrscr( ); printf("n. Enter the number: "); scanf("%d", &a); if(a>10) { printf(" n a is greater than 10"); } else { printf(" n a is less than 10"); } getch( ); } Output Enter the number: 2 a is less than 10

if. . else if statement Syntax if (condition 1) { Tstatements; } else if (condition 2) { Tstatements; } else if (condition 3) { Tstatements; } else { Fstatements; }

if. . else if statement TRUE Condition 1 FALSE TRUE TStatements Condition 2 FALSE TRUE TStatements Condition 3 FALSE FStatements

Example #include<stdio. h> #include<conio. h> void main() { int m 1, m 2, m 3; float avg; printf("n. Enter 3 marks: "); scanf("%d%d%d", &m 1, &m 2, &m 3); avg=(m 1+m 2+m 3)/3; printf("n The average is: %f", avg); printf("n The Grade is: "); if(avg>=60) { printf("First class"); } else if(avg>=50) { printf("Second class"); } else if(avg>=35) { printf("Thrid class"); } else { printf("Fail"); } getch(); } Output Enter 3 marks: 65 75 70 The average is: 70. 000000 The Grade is: First class

Example: 3 (if-else) #include <stdio. h> void main() { int invalid_operator = 0; char operator; float number 1, number 2, result; printf("Enter two numbers and an operator in the formatn"); printf(" number 1 operator number 2n"); scanf("%f %c %f", &number 1, &operator, &number 2); if(operator == '*') result = number 1 * number 2; else if(operator == '/') result = number 1 / number 2; else if(operator == '+') result = number 1 + number 2; else if(operator == '-') result = number 1 - number 2; else invalid _ operator = 1; if( invalid _ operator != 1 ) printf("%f %c %f is %fn", number 1, operator, number 2, result ); else printf("Invalid operator. n"); }

Nested if. . else Syntax if (condition 1) { if (condition 2) { True statements; } else { False statements; } } else { False statements 2; } If Condition 1 True statements If Condition 2 False Statements 2 False statements

Example: 4 (Nested-if) if(x > 0) { if(y > 0) printf("Northeast. n"); else printf("Southeast. n"); } else { } if(y > 0) printf("Northwest. n"); else printf("Southwest. n");

Switch Case • Multi way decision. It is well structured, but can only be used in certain cases; • Only one variable is tested, all branches must depend on the value of that variable. The variable must be an integral type. (int, long, short or char). • Each possible value of the variable can control a single branch. A default branch may optionally be used to trap all unspecified cases.

switch-case structure Syntax switch (expression) { case constant 1: block 1; break; case constant 2: block 2; break; . . default : default block; break; } switch(expression) case 1: case 2: default:

Example: switch-case #include<stdio. h> #include<conio. h> void main() { int i, n; printf("n. Enter the Number: "); scanf("%d", &n); switch(n) { case 1: { printf("n Its in case 1"); break; } case 2: { printf("n Its in case 2"); break; } default: { printf("n Its in default"); break; } } getch(); } Output: Enter the Number: 2 Its in case 2

Looping structure Ø It is used to execute set of instructions in several time based on condition. Ø while – The while loop evaluates the test expression. – If the test expression is true (nonzero), codes inside the body of while loop is executed. The test expression is evaluated again. The process goes on until the test expression is false. – When the test expression is false, the while loop is terminated. Ø do…while – The code block (loop body) inside the braces is executed once. – Then, the test expression is evaluated. If the test expression is true, the loop body is executed again. This process goes on until the test expression is evaluated to 0 (false). – When the test expression is false (nonzero), the do. . . while loop is terminated.

Looping structure Ø for – The initialization statement is executed only once. – Then, the test expression is evaluated. If the test expression is false (0), for loop is terminated. But if the test expression is true (nonzero), codes inside the body of for loop is executed and the update expression is updated. – This process repeats until the test expression is false.

while loop Syntax. while(condition) {. Body of the loop; . } condition True Body of The loop False

do…while Loop Syntax do { Body of the loop } while (condition); Body of The loop True condition False

Syntax - for loop for (initialization; condition; Increment/Decrement) { Body of the loop } Initialization Inc / Decrement Body of the loop condition false True

Example: 6 (while) int x = 2; while(x < 100) { printf("%dn", x); x = x * 2; } Example: 7 (for) int x; for(x=2; x<100; x*=2) printf("%dn", x); Example: 8 (do-while) do{ printf("Enter 1 for yes, 0 for no : "); scanf("%d", &input_value); } while (input_value == 1);

Calculate factorial using while & for #include<stdio. h> #include<conio. h> void main() { int i=1, fact=1, n; printf("n. Enter the Number: "); scanf("%d", &n); while(i<=n) { fact =fact *i; i++; // i=i+1 } printf("n The value of %d! is: %d", n, fact); getch(); } Output Enter the Number: 3 The value of 3! is: 6 for(i=1; i<=n; i++) { fact =fact *i; }

// add numbers until user enters zero using do-while #include <stdio. h> void main() { double number, sum = 0; do { printf("Enter a number: "); scanf("%lf", &number); sum += number; } while(number != 0. 0); printf("Sum = %. 2 lf", sum); }

Syntax goto label; . . . . label: statement; goto Syntax label: statement; . . . . goto label; -used to alter the normal sequence of a C program. -The label is an identifier. -When goto statement is encountered, control of the program jumps to label: and starts executing the code.

The break Statement • It is used to exit from a loop or a switch, • Control passing to first statement beyond the loop or switch. • Force an early exit from the loop • Protected by an if statement The continue Statement • It only works within • Force an immediate jump to loop control statement. • In a while loop & do while loop, jump to the test statement. • In a for loop, jump to increment/decrement then test, and perform the iteration. • Protected by an if statement.

Example: 9 (continue & break) int i; for (i=0; i<10; i++) { if (i==5) continue; printf("%d", i); if (i==8) break; } This code will print 1 to 8 except 5.

Input/Output Function Input/output Function Formatted Unformatted Input Output scanf() fscanf() printf() fprintf() getc() gets() getchar() putc() puts() putchar()

IO Statements The Standard Input Output File • Character Input / Output – getchar, getc – putchar, putc • Formatted Input / Output – printf – scanf • Whole Lines of Input and Output – gets – puts

Formatted Input/Output Ø Ø Ø C uses two functions formatted input and output. Formatted input : reads formatted data from the keyboard. Formatted output : writes formatted data to the monitor.

Formatted Input and Output

Format of printf Statement

Formatted Input (scanf) Ø The standard formatted input function in C is scanf (scan formatted). Ø scanf consists of : Ø a format string. Ø an address list that identifies where data are to be placed in memory. scanf ( format string, address list ); (“%c…. %d…. . %f…. . ”, &a, …. &i, …. . , &x…. . )

Format of scanf Statement

printf • More structured output than putchar. • Arguments: a control string (which controls what gets printed) and a list of values to be substituted for entries in the control string Example: int a, b; printf(“ a = %d, b=%d”, a, b); • possible to insert numbers into the control string to control field widths for values to be displayed. Example ü %6 d would print a decimal value in a field 6 spaces wide ü %8. 2 f would print a real value in a field 8 spaces wide with room to show 2 decimal places. • Display is left justified by default, but can be right justified by putting a - before the format information Example %-6 d, a decimal integer right justified in a 6 space field

scanf • Formatted reading of data from the keyboard. • Arguments-control string, followed by the list of items to be read. • Wants to know the address of the items to be read, the names of variables are preceded by & sign. • Character strings are an exception to this. Example: int a, b; scan f(“%d%d”, &a, &b);

getchar • It returns the next character of keyboard input as an int. • If there is an error then EOF (end of file) is returned instead. • Always compare this value against EOF before using it. • If the return value is stored in a char, it will never be equal to EOF, so error conditions will not be handled correctly. • As an example, here is a program to count the number of characters read until an EOF is encountered. • EOF can be generated by typing Control - d.

Example: (getchar) #include <stdio. h> void main() { int ch, i = 0; while((ch = getchar()) != EOF) i ++; printf("%dn", i); }

putchar • It puts the character argument on the standard output (usually the screen). • The following example program converts any typed input into capital letters. #include <ctype. h> #include <stdio. h> void main() { char ch; while((ch = getchar()) != EOF) putchar (toupper(ch)); }

gets • It reads a whole line of input into a string until a new line or EOF is encountered. • It is critical to ensure that the string is large enough to hold any expected input lines. • When all input is finished, NULL as defined in studio is returned. #include <stdio. h> main() { char ch[20]; gets(x); puts(x); }

puts • It writes a string to the output, and follows it with a new line character. • putchar, printf and puts can be freely used together #include <stdio. h> main() { char line[256]; /* large to store a line of input */ while(gets(line) != NULL) /* Read line */ { puts(line); /* Print line */ printf("n"); /* Print blank line */ } }

C - PREPROCESSOR • The C preprocessor, often known as cpp C Source code Preprocessor Compiler • It is a macro preprocessor (allows you to define macros, which are brief abbreviations for longer constructs) that transforms your program before it is compiled. • These transformations can be inclusion of header file, macro expansions etc. • Begins with a # symbol. • The C preprocessor is intended to be used only with C, C++, and Objective-C source code. Eg: #define PI 3. 14

Common Uses of cpp • • • Inclusion of Header files Macros Conditional Compilation Diagnostics Line control Pragmas

Include Syntax • Both user and system header files are included using the preprocessing directive `#include'. • Replace the file inclusion line with content of included file #include <file name> • This variant is used for system header files. • It searches for a file named file in a standard list of system directories. Eg: #include<stdio. h> #include "file name" • This variant is used for header files of your own program. • It searches for a file named file first in the directory containing the current file, then in the quote directories and then the same directories used for <file>. Eg: #include “user_header. h”

Macros using #define PI 3. 14 X=PI*2; expanded like X=3. 14*2; #define NUMBERS 1, 2, 3 int x[] = { NUMBERS }; expanded like int x[] = { 1, 2, 3 }; #define circle. Area(r) (3. 1415*r*r) X=circle. Area(5); expands to X=3. 1415*5*5;

Assign currently in effect #define TABLESIZE BUFSIZE #define BUFSIZE 1024 #define BUFSIZE 1020 #define TABLESIZE BUFSIZE #undef BUFSIZE #define BUFSIZE 37

Function-like Macros #include <stdio. h> #define PI 3. 1415 // #define circle. Area(r) (PI*r*r) void main() { float radius, area; printf("Enter the radius: "); scanf("%d", &radius); area = PI*radius; // area = circle. Area(radius); printf("Area=%. 2 f", area); }

Conditional Compilation • Instruct preprocessor whether to include certain chuck of code or not • Similar like a if statement. But big difference exist. (if- block of code gets executed or not; conditional if-block of code is included/ skipped for execution) • Use different code depending on the machine, OS • Compile same source file in two different programs • To exclude certain code from the program but to keep it as reference for future purpose

Conditional directives #ifdef MACRO conditional codes #endif #if expression conditional codes #elif expression 1 conditional codes if expression is non-zero #else conditional if expression is 0 #endif

#if defined BUFF_SIZE && BUFF_SIZE >= 2048 conditional codes

Predefined Macros Predefined macro Value __DATE__ String containing the current date __FILE__ String containing the file name __LINE__ Integer representing the current line number __STDC__ If follows ANSI standard C, then value is a nonzero integer __TIME__ String containing the current date.

#include <stdio. h> void main() { printf("Current time: %s", __TIME__); } O/P: Current time: 19: 54: 39

Enumeration • User-defined data type that consists of integral constants. • To define - keyword enum is used enum flag { const 1, const 2, . . . , const. N }; • Default values of enum elements is 0, 1 so on enum suit { club = 0, diamonds = 10, hearts = 20, spades = 3, };

Enumerated Type Declaration • When declaration of an enumerated type, only blueprint for the variable is created. enum boolean { F, T}; enum boolean check; enum boolean { F, T} check; • Enum variable takes only one value out of many possible values. • Good choice to work with flags enum suit card ; card = club; printf("Size of enum variable = %d bytes", sizeof(card));