Lab46 Wiki

Pointers to me are used as a way of referencing something without calling it directly, and they are useful as I have seen because you can change the location a pointer points at depending on the situation and outcome you desire. You could even use an array of pointers to complete a task. I look at pointers as a reference or indirect direct way to change and manipulate something without using the thing that is being changed or manipulated.

To use pointers, there are a couple of things to consider:

• Address of: *value = &x (Pointing value (a pointer) to the address of the variable x)
• Dereferencing: *value (* denotes the dereference of a variable, making it a pointer) (This makes it container less)
• Assignment: You will notice below with a demonstration how to assign a pointer. (char *value; value = (char *)malloc(sizeof(char)*4);)

To demonstrate pointers, I will show a code block using pointers and its output.

#include <stdio.h>                                                                                      
#include <stdlib.h>                                                                                    
 
int main(){                                                                                             
        char *value, i;                                                                                 
        value = (char *)malloc(sizeof(char)*4);                                                         
        *(value+0)=0;                                                                                   
        *(value+1)=1;                                                                                  
        fprintf(stdout, "Please enter a value (-128 - +127): ");                                       
        fscanf(stdin, "%hhd", &i);                                                                      
        *(value+2)=i;                                                                                   
        *(value+3)=(2*i)+3;
        for (i = 0; i <= 3; i++){                                                                       
                printf("%hhd\n", *(value+i));
        }                                                                                               
        return(0);                                                                                     
} 

lab46:~$ gcc -o prog7 prog7.c
lab46:~$ ./prog7
Please enter a value (-128 - +127): 8                                                                   
0                                                                                                       
1
8                                                                                                       
19
lab46:~$ 

Selection Structures are conditional statements that determine a path to take depending on the state of the condition. (True/False)

To demonstrate a Selection Structure, I will be using the If Selection Structure.

if (input > 4 || input < 0){
   printf("You have entered an incorrect value.\n");
   check = false;
}else{
   for (i = 0; i < argc; i++){
   printf("argv[%hhu][%hhu]: %c\n", i, input, *(*(argv+i)+input));
}

Repetition/Iteration Structures are a way of repeating certain contents of code until a condition is satisfied. They are usually defined mostly by whether a statement is True or False, and in the case of a while, as long as the statement is True, the while will continue to iterate.

As a demonstration, I will show a code example of a while loop and a for loop.

while (check == false){
   printf("Enter a value (0-4):");
   scanf("%d", &input);
   if (input > 4 || input < 0){
      printf("You have entered an incorrect value.\n");
      check = false;
   }else{
      for (i = 0; i < argc; i++){
         printf("argv[%hhu][%hhu]: %c\n", i, input, *(*(argv+i)+input));
      }
      check = true;
   }
}

Header Files are files that are applied to c code to incorporate libraries for use of their functions and data structures.

This demonstration will show a couple header files being included in a c code environment.

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

Logic and operators include devices for comparing and assigning variables. For example: int x = 0 (The '=' assigns the integer value of 0 to the integer variable x).

Demonstration for this keyword will include using AND (&&), OR (||), GREATER THAN (>), LESS THAN (<), and the Assignment Operator ( = ).

if (input > 4 || input < 0){
   check = false;
}
if (input > 4 && input < 0){
   check = true;
}

Arrays can be thought of as containers with indexes to each element in their ordered container. The ability to store data separately within a container and be able to access it easily with an index is the reason why Arrays are so useful. Arrays to me are dynamic storage containers with easily accessed schemes of data.

In this demonstration, I will be showing in c code some different Array types.

int argc; //Array of integers
char **argv; //Array of character pointers
int x[2]; //Array of integers with a size of 2
int t[2][2]; //Multidimensional Array with a Row size of 2 and Column size of 2

Standard I/O is a library of input, output, and error message types to be prompted to the terminal screen. Standard I/O must be included in a programming file such as .c for its input, output, and error message functions to work.

What follows is a demonstration of including Standard I/O to a .c file and using some of its functions to perform prompting tasks.

#include <stdio.h>
 
fprintf(stdout, "Please enter a value (-128 - +127): ");
fscanf(stdin, "%hhd", &i);

Functions as used by me are a set of instructions that can be defined by a name and referenced by the main part of a program to complete some sort of sub task to a greater full task.

Here is an example of functions in the language c:

  1 #include <stdio.h>
  2
  3 int sum(int, int, int, int);
  4 float average(int, int, int, int);
  5
  6 int main(){
  7         int a, b, c, d, high, low;
  8         a = b = c = d = 0;
  9         printf("Enter first value: ");
 10         fscanf(stdin, "%d", &a);
 11         printf("Enter second value: ");
 12         fscanf(stdin, "%d", &b);
 13         if (a > b){
 14                 high = a;
 15                 low = b;
 16         }else{
 17                 low = a;
 18                 high = b;
 19         }
 20         printf("Enter third value: ");
 21         fscanf(stdin, "%d", &c);
 22         if (c > high){
 23                 high = c;
 24         }else{
 25                 if (c < low){
 26                         low = c;
 27                 }
 28         }
 29         printf("Enter fourth value: ");
 30         fscanf(stdin, "%d", &d);
 31         if (d > high){
 32                 high = d;
 33         }else{
 34                 if (d < low){
 35                         low = d;
 36                 }
 37         }
 38         fprintf(stdout, "The sum of %d, %d, %d, and %d is: %d\n", a, b, c, d, sum(a, b, c, d));
 39         fprintf(stdout, "The average of %d, %d, %d, and %d is: %f\n", a, b, c, d, average(a, b, c, d));
 40         fprintf(stdout, "The highest input is: %d\n", high);
 41         fprintf(stdout, "The lowest input is: %d\n", low);
 42         return(0);
 43 }
 44
 45 int sum(int n1, int n2, int n3, int n4){
 46         return(n1 + n2 + n3 + n4);
 47 }
 48
 49 float average(int n1, int n2, int n3, int n4){
 50         return((float)(n1 + n2 + n3 + n4)/4);
 51 }

Write and compile code that utilizes programming constructs.

This objective entails the use of nano or vi along with the use of gcc to write and compile code within a certain standard of syntax and purpose.

The method to which I will use to measure my success in this objective is to show the steps and examples of how I have already completed this objective.

Steps to completing this objective include:

1. The use of nano or vi to edit text and create a .c file type.

lab46:~$ nano test.c 

lab46:~$ vim test.c 

#include <stdio.h>
 
int main()
{
    printf("Testing a printf.");
    return(0);
}

2. The use of gcc to compile code and check the syntax of the code.

lab46:~$ gcc -o test test.c
lab46:~$ 

3. Testing the code by running the file that I have compiled the .c file to.

lab46:~$ ./test
Testing a printf.
lab46:~$ 

Reflections:

• I believe I have done well and have shown success in this objective.
• I believe the room for improvement lays in the matter of programming constructs.
• I believe the measurement could be more effective with code examples as I have used above.
• I do have the belief that this would be an effective and simple employment.
• I do not believe the course objective should be altered in any way.