Week 06 Tutorial Questions

Part 1: Tutorial Performance Hurdle,

So far in this course we have only used scanf and printf to scan input and print output in our programs.

• How do we use getchar and putchar? How does getchar signal to us that it has reached the end of the input?

• Why does getchar return an int instead of a char?

• How do we use fgets? How does fgets signal to us that it has reached the end of the input?

• When fgets scans in a line of text, will it include a '\n' at the end of the line? Is this always the case?

• What does the following function do?

  int secret_function(char *word) {
      int i = 0;
      int result = 0;
      while (word[i] != '\0') {
          if (word[i] >= 'a' && word[i] <= 'z') {
              result++;
          }
          i++;
      }
      return result;
  }
  

• Can you explain the stopping case in the while loop? Why does it work and what is the significance of the '\0'?

#include <stdio.h>

int main(void) {
    char str[10];
    str[0] = 'H';
    str[1] = 'i';
    printf("%s", str);
    return 0;
}

What will happen when the above program is compiled and executed?

• How do you correct the program?

• Write a program sum_digits.c which reads characters from its input and counts digits.

  When the end of input is reached it should print a count of how many digits occurred in its input and their sum.

  The only functions you can use are getchar, printf and a very useful function called isdigit() from the ctype.h library which you should #include.

• strlen is a function that returns the length of a string. Write your own C function myStrlen to do the same.

int myStrlen(char string[]);

Part 2: Command line arguments

Tutor demo!

In this section we'll have a look at command line arguments and how they can be used to pass input to a C program when it is executed.

We'll be using this starter code:

#include <stdio.h>

int main(int argc, char *argv[]) {

    return 0;
}

The following diagram may be useful as a guide for explaining how command line arguments work:

Your turn!

In groups we will write pseudocode or a flowchart for one of the following programs:

Sum of Command Line Arguments: Write a C program that takes multiple integers as command-line arguments and prints their sum.

Count Characters in Command Line Arguments: Write a C program that counts the total number of characters in all the command-line arguments passed to it.

Reverse Command Line Arguments: Write a C program that prints all the command-line arguments passed to it in reverse order.

Check for Command Line Arguments: Write a C program that checks if any command-line arguments were provided except for the program name. If none were provided, print a message indicating so; otherwise, print the number of arguments.