C Tutorial/printf scanf/scanf Basics

Pass pointer argument to scanf

<source lang="cpp">#include <stdio.h> int main(void) {

 int value = 0;
 int *pvalue = NULL;
 pvalue = &value;                    /* Set pointer to refer to value  */
 printf ("Input an integer: ");
 scanf(" %d", pvalue);              /* Read into value via the pointer */
 printf("\nYou entered %d\n", value);
 return 0;

}</source>

Input an integer: string
     
     You entered 0

Reading and discarding characters from the input stream

<source lang="cpp">#include <stdio.h> int main() {

  int month1; 
  int day1;   
  int year1;  
  int month2; 
  int day2;   
  int year2;  
  
  printf( "Enter a date in the form mm-dd-yyyy: " );
  scanf( "%d%*c%d%*c%d", &month1, &day1, &year1 );
  printf( "month = %d  day = %d  year = %d\n\n", month1, day1, year1 );
  
  printf( "Enter a date in the form mm/dd/yyyy: " );
  scanf( "%d%*c%d%*c%d", &month2, &day2, &year2 );
  
  printf( "month = %d  day = %d  year = %d\n", month2, day2, year2 );
  return 0; 

}</source>

Enter a date in the form mm-dd-yyyy: 01-01-2001
month = 1  day = 1  year = 2001
Enter a date in the form mm/dd/yyyy: 01/01/2002
month = 1  day = 1  year = 2002

scanf

The scanf function: read information from a standard input device (keyboard).

<source lang="cpp">scanf("conversion specifier", variable);</source>

The conversion specifier argument tells scanf how to convert the incoming data.

1. scanf starts with a string argument and may contain additional arguments.
2. Additional arguments must be pointers.
3. scanf returns the number of successful inputs.

Common Conversion Specifiers Used with Scanf

Conversion Specifier Description %d Receives integer value %f Receives floating-point numbers %c Receives character

The scanf placeholders

d, i Used for signed integers; the expected argument should be a pointer to int.

<source lang="cpp">#include <stdio.h> main() {

   int i = 0;
   int k;
   printf("input an integer:\n");
   i=scanf("%d",&k);
   printf("total values inputted %d\n",i);
   printf("The input values %d\n",k);

}</source>

input an integer:
      3
      total values inputted 1
      The input values 3

Use scanf to get input from a standard input device, such as a keyboard

In scanf, you have to specify the address of a variable, such as &i, &j, and a list of format specifiers (%d). The number of format specifiers must be the same as the number of variables.

<source lang="cpp">#include <stdio.h> main(){

 int i,j,k;
 printf("Input two integers and press Enter to comfirm:");
 scanf("%d%d",&i,&j);
 k = i + j;
 printf("sum of two numbers is %d \n",k);

}</source>

Input two integers and press Enter to comfirm:223
     2
     sum of two numbers is 225

Using an inverted scan set

<source lang="cpp">#include <stdio.h> int main() {

  char z[ 9 ]; 
  
  printf( "Enter a string: " );
  scanf( "%[^aeiou]", z ); 
  printf( "The input was \"%s\"\n", z );
  return 0;

}</source>

Enter a string: string
The input was "str"

Using Scanf to Receive Input from a User

<source lang="cpp">#include <stdio.h> main(){

 int iOperand1 = 0;
 int iOperand2 = 0;
 printf("\nEnter first operand: ");
 scanf("%d", &iOperand1);
 printf("Enter second operand: ");
 scanf("%d", &iOperand2);
 printf("The result is %d\n", iOperand1+iOperand2);

}</source>

Enter first operand: 1
      Enter second operand: 2
      The result is 3