STANDARD INPUTOUTPUT Lecture 9 Motivation Standard IO refers

STANDARD INPUT/OUTPUT Lecture 9

Motivation • Standard I/O refers to the places where most data is either read from, the keyboard, or written to, the video monitor. • standard header for input/output: #include <stdio. h>

Basic I/O • There a couple of function that provide basic I/O facilities. • Probably the most common are: getchar() and putchar(). They are defined and used as follows: – int getchar(void) -- reads a char – int putchar(char ch) -- writes a char, returns character written.

/* SIMPLEIO. C */ #include <stdio. h> /* standard header for input/output */ int main() { int c; printf(“Masukkan sembarang karakter, X = program berhenti. n"); do { c = getchar(); /* get a single character from the kb */ putchar(c); /* display the character on the monitor */ } while (c != 'X'); /* until an X is hit */ printf("Program selesai. n"); return 0; }

Result of execution Masukkan sembarang karakter, X = program berhenti. (Output tergantung pada apa yang Anda ketik. ) Program selesai.

Printf • The function is defined as follows: – int printf(char *format, arg list. . . ) -- prints to stdout the list of arguments according specified format string. Returns number of characters printed. • The format string has 2 types of object: – ordinary characters -- these are copied to output. – conversion specifications -- denoted by % and listed in Table below.

Table: Printf/scanf format characters Format Spec (%) Type Result c Char Single character i, d Int Decimal number O Int Octal number X, x Int Hexadecimal number Lower/uppercase notation u Int Unsigned int

Table: Printf/scanf format characters Format Spec (%) Type Result s *char Print string Terminated by 0 f Double/float Format –m. ddd. . . E, e " Scientific format -1. 23 e 002 g, G " e or f whichever % - print % character

Between % and format char we can put: - (minus sign) -- left justify. integer number -- field width. m. d -- m = field width, d = precision of number of digits after decimal point or number of chars from a string. So: printf("%-2. 3 f n", 17. 23478); The output on the screen is: 17. 235 and: printf("VAT=17. 5%% n"); . . . outputs: VAT=17. 5%

scanf This function is defined as follows: int scanf(char *format, args. . ) -- reads from stdin and puts input in address of variables specified in args list. Returns number of chars read. Format control string similar to printf Note: The ADDRESS of variable or a pointer to one is required by scanf(``%d'', &i); We can just give the name of an array or string to scanf since this corresponds to the start address of the array/string. char string[80]; scanf(``%s'', string);

CHARACTER STRING INPUT

/* Program - INTIN. C */ #include <stdio. h> int main() { int valin; printf(“Masukkan angka dari 0 sampai 32767, stop jika 100. n"); do { scanf("%d", &valin); /* read a single integer value in */ printf("The value is %dn", valin); } while (valin != 100); printf("End of programn"); return 0; }

Result of execution Masukkan angka dari 0 sampai 32767, stop jika 100. (The output depends on the numbers you type in. ) End of program

IN Memory I/O

• /* Program - INMEM. C */ #include <stdio. h> int main() { int numbers[5], result[5], index; char line[80]; numbers[0] = 74; numbers[1] = 18; numbers[2] = 33; numbers[3] = 30; numbers[4] = 97; sprintf(line, "%d %d %dn", numbers[0], numbers[1], numbers[2], numbers[3], numbers[4]); printf("%s", line); sscanf(line, "%d %d %d", &result[4], &result[3], (result+2), (result+1), result); for (index = 0 ; index < 5 ; index++) printf("The final result is %dn", result[index]); return 0; }

Result of execution 74 18 33 30 97 The final result is 30 The final result is 33 The final result is 18 The final result is 74

FILE INPUT/OUTPUT

/* Program - FORMOUT. C */ #include <stdio. h> #include <string. h> int main() { FILE *fp; char stuff[25]; int index; fp = fopen("TENLINES. TXT", "w"); /* open for writing */ strcpy(stuff, "This is an example line. "); for (index = 1 ; index <= 10 ; index++) fprintf(fp, "%s Line number %dn", stuff, index); fclose(fp); /* close the file before ending program */ return 0; }

Result of execution (The following is written to the file named TENLINES. TXT) This is an example line. Line number 1 This is an example line. Line number 2 This is an example line. Line number 3 This is an example line. Line number 4 This is an example line. Line number 5 This is an example line. Line number 6 This is an example line. Line number 7 This is an example line. Line number 8 This is an example line. Line number 9 This is an example line. Line number 10

/* Program - CHAROUT. C */ #include <stdio. h> #include <string. h> #include <stdlib. h> int main() { FILE *point; char others[35]; int indexer, count; strcpy(others, "Additional lines. "); point = fopen("tenlines. txt", "a"); /* open for appending */ if (point == NULL) { printf("File failed to openn"); exit (EXIT_FAILURE); } for (count = 1 ; count <= 10 ; count++) { for (indexer = 0 ; others[indexer] ; indexer++) putc(others[indexer], point); /* output one character */ putc('n', point); /* output a linefeed */ } fclose(point); return EXIT_SUCCESS; }

Result of output (appended to TENLINES. TXT) Additional lines.

READING A FILE

/* Program - READCHAR. C */ #include <stdio. h> #include <stdlib. h> int main() { FILE *funny; int c; funny = fopen("TENLINES. TXT", "r"); if (funny == NULL) { printf("File doesn't existn"); exit (EXIT_FAILURE); } else { do { c = getc(funny); /* get one character from the file */ putchar(c); /* display it on the monitor */ } while (c != EOF); /* repeat until EOF (end of file) */ } fclose(funny); return EXIT_SUCCESS; }

Result of execution This is an example line. Line number 1 This is an example line. Line number 2 This is an example line. Line number 3 This is an example line. Line number 4 This is an example line. Line number 5 This is an example line. Line number 6 This is an example line. Line number 7 This is an example line. Line number 8 This is an example line. Line number 9 This is an example line. Line number 10 Additional lines.

READING A WORD AT A TIME

/* Program - READTEXT. C */ #include <stdio. h> int main() { FILE *fp 1; char oneword[100]; int c; fp 1 = fopen("TENLINES. TXT", "r"); do { c = fscanf(fp 1, "%s", oneword); /* get one word from file */ printf("%sn", oneword); /* display it on the monitor */ } while (c != EOF); /* repeat until EOF */ fclose(fp 1); return 0; }

Result of execution This is an example line. Line number 1 This is an . . . (Many other lines). . . Additional lines.

HOW TO USE A VARIABLE FILENAME

/* Program - ANYFILE. C */ #include <stdio. h> #include <stdlib. h> int main() { FILE *fp 1; char oneword[100], filename[25]; char *c; printf("Enter filename -> "); scanf("%s", filename); /* read the desired filename */ fp 1 = fopen(filename, "r"); if (fp 1 == NULL) { printf("File failed to openn"); exit (EXIT_FAILURE); } do { c = fgets(oneword, 100, fp 1); /* get one line from the file */ if (c != NULL) printf("%s", oneword); /* display it on the monitor */ } while (c != NULL); /* repeat until NULL */ fclose(fp 1); return EXIT_SUCCESS; }

Result of execution (The file selected is listed on the monitor)

HOW DO WE PRINT?

/* Program - PRINTDAT. C */ #include <stdio. h> #include <stdlib. h> int main() { FILE *funny, *printer; int c; funny = fopen("TENLINES. TXT", "r"); /* open input file */ if (funny == NULL) { printf("File failed to openn"); exit (EXIT_FAILURE); } printer = fopen("PRN", "w"); /* open printer file */ if (printer == NULL) { printf("Printer not available for usen"); exit (EXIT_FAILURE); } do { c = getc(funny); /* get one character from the file */ if (c != EOF) { putchar(c); /* display it on the monitor */ putc(c, printer); /* print the character */ } } while (c != EOF); /* repeat until EOF (end of file) */ fclose(funny); fclose(printer); return 0; }

Result of execution (The file named TENLINES. TXT is listed on the printer, and it is listed on the monitor. )