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.

Explore the fundamentals of static arrays in this lecture from the DT143G course. Dive into the concepts of data structures, their reliance on variables, and the use of loops within the context of programming. This session also emphasizes the importance of arrays in managing homogenous data efficiently.