#include < stdio.h>

int main()
{
    int week;
    
    /* Input week number from user */
    printf("Enter week number(1-7): ");
    scanf("%d", &week);
    
    switch(week)
    {
        case 1: 
            printf("Monday");
            break;
        case 2: 
            printf("Tuesday");
            break;
        case 3: 
            printf("Wednesday");
            break;
        case 4: 
            printf("Thursday");
            break;
        case 5: 
            printf("Friday");
            break;
        case 6: 
            printf("Saturday");
            break;
        case 7: 
            printf("Sunday");
            break;
        default: 
            printf("Invalid input! Please enter week number between 1-7.");
    }

    getch();
}

Program Explanation

Step 1 : Include header files (#include< stdio.h> and #include< conio.h>).

Step 2 : Start with main function with return type.

Step 3 : parenthesis to start and end the program { }.

Step 4 : declare variables with data type i.e, 'Week' is an integer type so we use "int" data type.

Step 5 : Use output function printf() to print the output on the screen.

Step 6 : Use input function scanf() to get input from the user.

Step 7 : here, we have print week of the day using switch case, enter a week no.(1 to 7) only. we have press 1. it was go to case 1. then the statement was right. then print "Monday". we can not enter between 1 to 7 then print "Invalid input! Please enter week number between 1-7."

Step 8 : using getch() function to hold the screen.