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Input Output in C

Input Output​

  • Input and output refer to the process of reading data from a source, say user input (shell) or file and displaying data to a destination, say computer console (shell) or file.

  • In C, input is usually provided by the user or by an external device, while output is typically displayed on the computer screen or written to a file. There are several functions in C that are commonly used for input and output.

  • Some of the most frequently used ones include:

printf()​

This function is used to print data to the console or terminal window. It is used to display messages, numbers, and other values on the screen.

Syntax:

int scanf(const char *format, ...);
  • The first argument is a format string that specifies how to read the input, followed by pointers to variables where the input should be stored.
  • The function returns the number of input items successfully matched and assigned.

scanf()​

This function is used to read input data from the user. It is used to capture keyboard input from the user.

Syntax:

int scanf(const char *format, ...);
  • The first argument is a format string that specifies how to read the input, followed by pointers to variables where the input should be stored.
  • The function returns the number of input items successfully matched and assigned.

getchar()​

This function is used to read a single character from the user. It is used to capture single keystrokes from the keyboard.

Syntax:

int getchar(void);
  • It waits for the user to input a character and then returns that character as an integer.

putchar()​

This function is used to display a single character on the screen. It is used to output single characters to the console.

Syntax:

int putchar(int c);
  • This function is used to write a single character to the console.
  • The character to be printed is specified as an integer.

fread()​

This function is used to read data from a file. A file should be opened first before being able to read using fopen() and then close using fclose().

Syntax:

size_t fread(void *ptr, size_t size, size_t count, FILE *stream);
  • The first argument is a pointer to a buffer where the data will be stored.
  • The second argument is the size of each element to be read, the third argument is the number of elements to read, and the fourth argument is a pointer to the file to read from.
  • The function returns the number of elements successfully read.

fwrite()​

This function is used to write data to a file. A file should be opened first before being able to read using fopen() and then close using fclose().

Syntax:

size_t fwrite(const void *ptr, size_t size, size_t count, FILE *stream);
  • The first argument is a pointer to the data to be written
  • The second argument is the size of each element to be written
  • The third argument is the number of elements to write
  • The fourth argument is a pointer to the file to write to
  • The function returns the number of elements successfully written.