Lecture 8- Data Input and Output
- 1. Data Input and Output Md. Imran Hossain Showrov ([email protected]) 8 1
- 2. Outline Input/Output Functions Single Character Input Single Character Output The scanf Function The printf Function
- 3. Input/Output Functions There are several library functions which includes a number of input/output functions. Six common functions are: getchar, putchar, scanf, printf, get and puts. These six functions permit the transfer of information between the computer and the standard input/output devices.
- 4. Single Character Input- The getchar Functions Single character can be entered into the computer using getchar. It returns a single character from standard input device(typically keyboard). Can be represented as: character variable = getchar() Where, character variable refers to some previously declared character variable.
- 5. Single Character Input- The getchar Functions (cont..) Example: char c; ……… c = getchar(); The first statement declares that c is a character-type variable. The second statement causes a single character to be entered from the standard input device and then assigned to c.
- 6. Single Character Output- The putchar Functions Single character can be displayed using putchar. This function is complementary to the character input function getchar. It transmits a single character to a standard output device. Can be represented as putchar(character variable)
- 7. Single Character Output- The putchar Functions (cont..) Example: char c; ……… putchar(); The first statement declares that c is a character-type variable. The second statement causes the current value of c to be transmitted to the standard output device where it will be displayed.
- 8. Example 1: getchar and putchar #include<stdio.h> #include<ctype.h> main() { char ch; printf(“Enter any character value: ”); ch = getchar(); printf(“The equivalent upper case: ”); putchar(toupper(ch)); }
- 9. Example 1: getchar and putchar (cont..) This program converts lowercase to uppercase. Sample input: a Sample output: A Sample input: d Sample output: D Sample input: l Sample output: L
- 10. Entering Input Data- The scanf Function The scanf() function reads data from the standard input stream stdin into the locations given by each entry in argument-list. A non-whitespace character causes the scanf() function to read, but not to store, a matching non- whitespace character.
- 11. The scanf Function The skeletal structure is: #include<stdio.h> main() { int a,b,c; ………….. scanf(“%d %d %d”, &a, &b, &c); ……………….. }
- 12. The scanf Function (cont..) Consider the last skeleton- When the program is executed, three integer quantities will be entered 1 2 3 Then the following assignments will result: a = 1, b = 2, c = 3 If the data had been entered as 123 456 789 Than the assignment would be a = 123, b = 456, c = 789
- 13. The scanf Function (cont..) Example: #include<stdio.h> main() { int i; float x; char c; ……………. scanf(“%3d %5f %c”, &l, &x, &c); ……………………… }
- 14. The scanf Function (cont..) If the data items are entered as 10 256.875 T When the program is executed, then 10 will be assigned to I, 256.8 will be assigned to x and the character 7 will be assigned to c. The remaining two input characters (5 and T) will be ignored.
- 15. The printf Function Output data can be written from the computer onto a standard output device using the library function printf. printf(control string, arg1, arg2, ….. , argn) Where control string refers to a string that controls formatting information, and arg1, arg2…… argn are arguments that represent the individual output data items.
- 16. The printf Function (cont..) Commonly used conversion characters for data i/o
- 17. The printf Function (cont..) The following C program illustrates the use of the minimum field width feature, #include<stdio.h> main() { int i = 12345; float x = 345.678; printf(“%3d %5d %8dnn”,i,i,i); printf(“%3f %10f %13fnn”,x,x,x); }
- 18. The printf Function (cont..) When the program is executed, the following output is generated 12345 12345 12345 345.678000 345.678000 345.678000 The first and second line of output displays a decimal integer using three different minimum field widths.