C preprocesor

C preprocesor

• 1.
  • Preprocessor arecommands executed by C Preprocessor before the program is assigned to the compiler for compilation. • Preprocessor directives appear at the starting of the program. • It is also called as CPP.
• 3.
  #include • This isused to include header files in the link section area containing the functions to be used in a program. #include<stdio.h> This includes standard input output (stdio) header files of include subdirectory from a C directory.
• 4.
  • To compilea portion of program conditionally, then these directives are used. #ifdef(MAX) #define MIN 20 #else #define MAX 100 #define MIN 20 #endif
• 5.
  #if, #elif • Theseare used when there is branched conditions or nested conditions. Ex: #if code==30 printf(“color is red”); #elif code==40 printf(“code is blue”); #endif
• 6.
  #undef • This isused to undefine a macro which was earlier defined using #define statement. #pragma, ## • Pragma is used to write assembly language statements into C program. • ## is used to concatenate the items in the C language.
• 7.
  Input/ output statements •Input and output functions are collectively known as standard I/O library functions. • These statements deals with the console input/output function(input from computer and output on monitor), so called as console input/output functions. • Two types of I/O functions are: 1. unformatted I/O 2. formatted I/O
• 8.
  • 1. getchar(): an input function to read a single character. Syntax: v = getchar(); Ex: char m; m=getchar(); 2. putchar() : an output function to display a single character on screen. Syntax: putchar(v); Ex: char m; putchar(m);
• 9.
  3. gets() :an input function used to read a string from a keyboard. Syntax: gets(v); Ex: char m[10]; gets(m); 4. puts() : an output function used to display gets() inputted string on the screen. Syntax: puts(s); or puts(“text”); Ex: char name[20]; puts(“enter any name”); gets(name); puts(“the entered name is”); puts(name); Output: Enter any name Preeti The entered name is Preeti
• 10.
  5. getch() :an input function that reads a single character. In this, a character data read by this function is directly assigned to a variable. This even maintains output on the screen. Also, when character is typed ,it is not visible on the screen. Syntax: v=getch(); Ex: char x puts(“enter any character”); x=getch(); puts(“entered character is”); putchar(x); getch(); Output: Enter any character Entered character is g
• 11.
  6. getche() :when you type a character data from the keyboard it will be visible on the screen. Syntax: v=getche(); Ex: char x puts(“enter any character”); x=getche(); puts(“entered character is”); putchar(x); getche(); Output: Enter any character g Entered character is g
• 12.
  • It refersto an input/ output data. • Two types are: 1. scanf() 2. printf() 1. scanf() This is an input function. It is used to read a mixed type of data. Syntax: scanf(“control strings”, arg1,arg2,….argn); Or scanf(“control strings”,&v1,&v2….&vn);
• 13.
  Control strings havesome format code for different data types as follows: Ex: int a; scanf(“%d”,&a); Format code Meaning %c To read single character %d To read a signed decimal integer %f To read a float value %i To read an integer(octal, decimal, hexadecimal) %x To read a hexadecimal integer only %u To read pointers %s To read a string
• 14.
  2. printf() :This is an output function. It is used to display text message and a mixed type of data on the screen. Syntax: printf(“control strings”,v1,v2….vn); Or printf(“message line or text line”); Format code Meaning %c To print single character %d To print a signed decimal integer %f To print a float %x To print a hexadecimal integer only %u To print unsigned integers %s To print a string
• 15.
  • Ex: int a; floatb; printf(“enter the value”); scanf(“%d%f”,&a,&b); printf(“the data is”); printf(“%d%f”,a,b); Output: enter the value 5 6.0 the data is 5 6.0