Unformatted Input and Output Functions in C Language

Unformatted input and output functions read a single input sent by the user and permit the display of the value as the output at the console.

Unformatted input functions

The unformatted input functions in the C programming language are used only for character data type or character string/array and cannot be used for any other datatype. These functions are used to read a single input from the user and this allows the user to display the value at the console.

The getchar() Function

This getchar() function reads only the first single character from the given keyboard that multiplies characters is typed by the user and this function reads one character at a time until the enter key is pressed. This function is declared in stdio.h file.

The syntax of getchar() function is as follows ?

Variablename=getchar();

This code declares a character variable a and assigns it with the value returned by the getchar() function, which reads a single character from the standard input.

Char a;
a = getchar();

Example Program

The below example writes the user input to a file until EOF, then reads and prints the file's content word by word. This will also check the file before reading.

#include <stdio.h>

int main() {
   char ch;
   FILE *fp;
   fp = fopen("file.txt", "w");  // open the file in write mode
   printf("enter the text then press cntrl Z:
");
   while ((ch = getchar()) != EOF) {
      putc(ch, fp);
   }
   fclose(fp);
   fp = fopen("file.txt", "r");
   printf("text on the file:
");
   if (fp) {
      char word[100];
      while (fscanf(fp, "%s", word) != EOF) {  // read words from file
         printf("%s
", word);  // print each word on separate lines
      }
      fclose(fp);  // close file
   } else {
      printf("file does not exist
");  // tell the user that the file does not exist
   }
   return 0;
}

When the above program is executed, it produces the following result ?

enter the text then press cntrl Z:
This is an example program on getchar()
text on the file:
This
is
an
example
program
on
getchar()

The gets() Function

It reads a string from the keyboard by the user and these characters get stored in a character array. This function allows us to write separated texts or strings. This function is declared in stdio.h file. The syntax for gets() function is as follows ?

gets(variablename);

Example Program

#include <stdio.h>
#include <string.h>

int main() {
   char str[10];
   printf("Enter your name: 
");
   fgets(str, sizeof(str), stdin);
   // Remove newline character if present
   str[strcspn(str, "
")] = '\0';
   printf("Hello %s, welcome to Tutorialspoint", str);
   return 0;
}

Following is the output of the above program ?

Enter your name:
Madhu
Hello Madhu welcome to Tutorialspoint

Unformatted output functions

The unformatted output functions in C programming language are as follows ?

The putchar() Function

It displays a single character on the monitor, taking one character as input and writing it to the standard output. This function is commonly used in programs that require character-by-character output.

The syntax for putchar() function is as follows ?

Putchar(variablename);

The putchar('a); function prints the character 'a' to a standard output.

Putchar(?a');

The puts() Function

The puts() function displays a group of characters or strings stored in a character array on the monitor.

The syntax for puts() function is as follows ?

puts(variablename);

This function call prints the string "tutorial" specified by a character to the standard output.

puts("tutorial");

Example Program

Following is the C program for putc() and getc() functions ?

#include <stdio.h>

int main() {
    char ch;
    FILE *fp;
    fp = fopen("std1.txt", "w");
    printf("enter the text. press Ctrl+Z:
");
    while((ch = getchar()) != EOF) {
        putc(ch, fp);
    }
    fclose(fp);

    fp = fopen("std1.txt", "r");
    printf("text on the file:
");
    while((ch = getc(fp)) != EOF) {
        putchar(ch);
    }
    fclose(fp);

    return 0;
}

When the above program is executed, it produces the following result ?

enter the text.press cntrl Z:
This is an example program on putchar()
text on the file:
This is an example program on putchar()