Programming Techniques DT143G - Lecture 7

Programmeringsteknik DT143G - Lecture 7: Static Arrays

• Lecture: Arrays (static), given by Pascal Rebreyend on 26-11-2024.

Today's Contents

• Static Arrays
• Loops, revisited
• Homogenous data structures

Variables and Data

• Variables store local and temporary information during computations.
• Variables store data/information used as input or during the program.
• Problem: Variables only store one value.
• Variables are not suitable for large volumes of data (e.g., sound, video).

Data Structures

• Data structures define how data is stored and connected.
• They are an important aspect of programming.
• Examples include arrays and matrices.
• Files also have a structure.
• Other data structures will be covered later.

Arrays

• Arrays are one-dimensional structures.
• All elements have the same data type (e.g., float, integer).
• An array is a new data type based on previous ones.
• Array elements are accessed directly using an index (the first element has index 0).
• Example code (in C):

  #include <stdio.h>
  int main() {
    int a[10];
    a[4] = 4;
    printf("%d\n", a[4]);
    return 0;
  }
  

Arrays and Loops

• Loops are useful for working with arrays.
• Example code (in C):

  #include <stdio.h>
  int main() {
    int a[10], i;
    for (i = 0; i < 10; i++) {
      a[i] = i * 2;
    }
    for (i = 0; i < 10; i++) {
      printf("a[%d]=%d\n", i, a[i]);
    }
    return 0;
  }
  

Multidimensional Arrays

• Multidimensional arrays (like matrices) are possible.
• Example code (in C):

  #include <stdio.h>
  int main() {
    int a[10][5];
    int i, j;
    for (i = 0; i < 10; i++) {
      for (j = 0; j < 5; j++) {
        a[i][j] = i * 2 + j;
      }
    }
    for (i = 0; i < 10; i++) {
      for (j = 0; j < 5; j++) {
        printf("a[%d][%d]=%d\n", i, j, a[i][j]);
      }
    }
    return 0;
  }
  

Arrays and Functions

• Modifying an array within a function affects the original array (side effect).
• Arrays cannot be returned as the value of a function.
• Example code (in C):

  #include <stdio.h>
  void display(int b[]) {
    int i;
    for (i = 0; i < 10; i++) {
      printf("array[%d]=%d\n", i, b[i]);
    }
  }
  int main() {
    int a[10], i;
    for (i = 0; i < 10; i++) {
      a[i] = i * 2;
    }
      display(a);
    return 0;
  }
  

Size of Arrays

• Array size is fixed at compile time.
• Common practices for defining array size:
  • Using #define: #define SIZE 5.
  • Using compiler flags: gcc -DSIZE=5.

Conclusion

• Arrays are useful for manipulating sets of values.
• Array size is fixed during compilation.
• Arrays are used to group variables with the same type.