When we say Input, it means to feed some data into a program. An input can be given in the form of a file or from the command line. C programming provides a set of built-in functions to read the given input and feed it to the program as per requirement.

In the C programming language, scanf is a function that reads formatted data from stdin (i.e, the standard input stream, which is usually the keyboard, unless redirected) and then writes the results into the arguments given.

#include<stdio.h>

int main() {
    int a,b;
    printf("Enter the value of a\n");
    scanf("%d", &a); // & address of a;

    printf("Enter the value of b\n");
    scanf("%d", &b);

    printf("Sum of a and b is %d", a + b);
    
    return 0;
}

Standard input or stdin is used for taking input from devices such as the keyboard as a data stream. Standard output or stdout is used for giving output to a device such as a monitor. For using I/O functionality, programmers must include stdio header-file within the program.

An output function is a function that an optimization function calls at each iteration of its algorithm. Typically, you use an output function to generate graphical output, record the history of the data the algorithm generates, or halt the algorithm based on the data at the current iteration.