Input and Output

Output

C uses printf() to print output text or values to the console. printf() does not insert a new line at the end of the output.

Syntax:   printf("some random text") is used to print text inside the " ".

printf("format specifier", variable_name) is used to print the variable specified. Format specifier is used to specify which data type that you want to use. You can see what is a format specifier in the variable and data type page.

Example:

            

            
    #include <stdio.h>

    int main() {
        int myNum = 19;
        
        printf("Hello World!");
        printf("%d",myNum);
        return 0;
      } 
            
          
          

    Copy

          
        

Input

In C, you can use the scanf() function to get user input.

Syntax:   scanf("format specifier", &variable_name)

Format specifier is used to specify which data type that you want to use. You can see what is a format specifier in the variable and data type page. scanf() can also accept multiple inputs.

Example:

        

        
    #include <stdio.h>

    int main() {
        int myNum;
        char myChar;

        printf("Input a number and a character:");
        scanf("%d %c",&myNum, &myChar);
        return 0;
    } 
        
      
      

  Copy

      
    

scanf() can also take string input, but it will only accept the string until it sees a white space. To avoid this error, we use fgets(fullName, sizeof(fullName), stdin) instead of scanf(). We can still use scanf("%s", &variable_name) if the string does not contain any white space between the contents.

Example:

            

            
    #include <stdio.h>

    int main() {
        char myName[20];

        printf("Input a name:");
        fgets(myName, sizeof(myName), stdin);
        return 0;
    } 
            
          
          

    Copy

          
        

Comments

Comments can be used to explain what does a block of code do. Comments can also be used to prevent the execution of some lines of code. There are two types of comments in C:

• Single Line Comment

Any text between // and the end of the line will not be executed by the compiler.
Syntax: //some comments here

• Multiple Line Comments

Syntax:

            

            
      /*	Hello world!
          Some comment here
      */ 
            
          
          

    Copy

          
        

Example:

          

          
    #include <stdio.h>
  
    int main() {
      char myName[20];

      //this line will not be executed
      printf("Input a name:");
      fgets(myName, sizeof(myName), stdin);
      
      /*
      printf("hello")
      The console will not show "hello" because the
      printf("hello") is in the comment and will not 
      Be executed.
      */
      return 0;
    } 
          
        
        

  Copy

        
      

Escape Sequences

Escape sequences are mostly used to control or format the output.

Example:

        

        
    #include <stdio.h>
  
    int main() {
      printf("Hello,\nWorld!");

      /*The output will be
      Hello,
      World!
      Instead of 
      Hello,World!
      */

      return 0;
    }
        
      
      

  Copy

      
    

Below are the most commonly used escape sequences.