typedef and array

Learn to define array types with typedef.

typedef and array

typedef also names array types. Multi-dimensional arrays have complex syntax; typedef simplifies the code.

Example: typedef int Matrix[3][3];. This names a 3×3 integer matrix type Matrix. From then on you write Matrix m; instead of int m[3][3];. Each element is accessed as m[i][j]. This pattern is common in mathematical calculations and game board representation. The type name reflects the purpose; when someone writes Matrix, everyone expects a 3×3 integer matrix.

Matrix initialization

You initialize a Matrix variable with nested brace lists. Each inner list represents a row.

Example: Matrix m = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };. This lays out the numbers 1 through 9 in a 3×3 grid. m[0][0] = 1, m[1][1] = 5, m[2][2] = 9. Inner braces separate rows; they improve readability. This structure is the basis of matrix operations and tabular data. Thanks to typedef, it is declared concisely and meaningfully as Matrix.

Exercise Write a Matrix program

Define typedef int Matrix[3][3];. In main create Matrix m = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };. Print the center element with printf("%d\n", m[1][1]);.

Show example solution

#include <stdio.h>

typedef int Matrix[3][3];

int main(void) {
    Matrix m = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };
    printf("%d\n", m[1][1]);
    return 0;
}

Test yourself

Complete the matrix access

printf("%d
", m[1][____]);

Show answer

printf("%d
", m[1][1]);

Match the matrix indices

m[0][0]

Top left
m[1][1]

Center
m[2][2]

Bottom right
Matrix

Type name
What does typedef int Matrix[3][3]; define?
- A 3-element array
- A 3×3 integer matrix type
- A pointer type
- A function type
Show answer

A 3×3 integer matrix type — Matrix is a 3×3 integer two-dimensional array type.

Next lesson: Opaque types

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