An Introduction to C Programming Geb Thomas Learning

An Introduction to C Programming Geb Thomas

Learning Objectives n n n Learn how to write and compile a C program Learn what C libraries are Understand the C variable types Understand how to use if and if/else statements Understand how to use the for structure

How to Write and Compile C Programs n n n C, C++ and Java Compilers: Microsoft Visual C++, GCC, Borland C Since we will be working on PCs: n Microsoft Visual C++ n n Open new Win 32 Console Application Name it (in “project name”) Click “a hello world application” Go to file view, source files, then the name of your project. cpp

Some Things About C n n Case matters, white space does not Comments go between /* and */ Each statement is followed by a semicolon Execution begins in the main function: int main(int argc, char* argv[]) { /* ignore this */ /* start here */ return 0; /*end here */ }

What are C libraries? n n C is a lightweight language. Most of its intelligence is compartmentalized in libraries. Almost all c programs use the “stdio” or standard input/output library. Many also use the “math” library. To use a library, include the header file (I. e. , “stdio. h”) at the top of the file. For most special purpose libraries (I. e. , math) you need to include the library on the link line. In Visual C++, go to project->settings>object/module libraries.

C Variable Types n n n The most common types are: char, int, float, and double. Strings are arrays of characters (we’ll cover arrays later). Declare a variable before you use it: int x; /* declares an integer called x. Its value is not assigned. */ float y, z = 3. 14159; /* declares two floating point numbers. z is set equal to pi */ z = 4; /* now z is equal to 4 */ my. Val = 2; /* This would be an error, because my. Val was not yet declared */

Logical Operators n n C defines these logical operators: <, >, <=, >= and == (the equivalence operator) You can compare any variable. Characters are compared based on their ASCII values. All answers will be true (not zero) or false (0) You can extend the logic with && (and), ~ (not) and || (or).

The If Statement n n n Syntax: if (expression) statement; If the expression is true (not zero), the statement is executed. If the expression is false, it is not executed. You can group multiple expressions together with braces: if (expression) { statement 1; statement 2; statement 3; }

The If/Else Statement n n Syntax: if (expression) statement_1; else statement_2; If the expression is true, statement_1 will be executed, otherwise, statement_2 will be. if (my. Val < 3) printf(“my. Val is less than 3. n”); else printf(“my. Val is greater than or equal to 3. n”);

The For Loop n n Syntax: for (initialization; test; increment) {statements; } The for loop will first perform the initialization. Then, as long is test is TRUE, it will execute statements. After each execution, it will increment. for (cntr = 0; cntr < 3; cntr = cntr + 1) { printf(“ Counter = %dn”, cntr); } Counter = 0; Counter = 1; Counter = 2;

Learning Objectives n n n Learn how to write and compile a C program Learn what C libraries are Understand the C variable types Understand how to use if and if/else statements Understand how to use the for structure