--- title: "Pass array; transpose 3×3 matrix" subject: "Computer Programming" chapter: 7 key: "semester_1/computer_programming:pass-array-transpose-3x3" source: https://www.bctengineer.com/q/semester_1/computer_programming/pass-array-transpose-3x3 site: BCT Engineering --- # Pass array; transpose 3×3 matrix Computer Programming · Chapter 7: Arrays and Strings - Asked in: 2069 Chaitra, 2+6 marks - Video: [C_57 Two Dimensional Array program 2 | Program to print Transpose of Matrix](https://www.youtube.com/watch?v=EmqelMa54Y4) — Jenny's Lectures CS IT - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_1/computer_programming/pass-array-transpose-3x3 - Whole chapter: https://www.bctengineer.com/md/semester_1/computer_programming/chapter-7 ## Question Explain how array can be passed to a function. Write a program to transpose a 3*3 matrix. Two matrix are input from the main () function and pass to a user defined function with argument as array. The result is displayed from the main function. ## Short answer The array name gives the address. The transpose function copies element a[i][j] to t[j][i]. In main, read two 3×3 matrices, call transpose on each, and display the transposed matrices. ## Answer #### Passing an array to a function Only the array name is written in the function call, for example `transpose(a, t);`. The name gives the address of the first element, so the called function works on the original array (call by reference) and no copy is made. The parameter is declared as an array (`int a[3][3]`, or `int a[][3]`); for 2D arrays the column size is compulsory. Changes made to the array inside the function are visible in the caller. #### Program Both matrices are read in `main()` and passed to the function `transpose(a, t)`, which stores a[i][j] in t[j][i]. The transposed matrices are then displayed from `main()`. ```c #include void transpose(int a[3][3], int t[3][3]) { for (int i = 0; i < 3; i++) for (int j = 0; j < 3; j++) t[j][i] = a[i][j]; } int main(void) { int a[3][3], b[3][3], ta[3][3], tb[3][3]; printf("Enter first matrix (9 values): "); for (int i = 0; i < 3; i++) for (int j = 0; j < 3; j++) scanf("%d", &a[i][j]); printf("Enter second matrix (9 values): "); for (int i = 0; i < 3; i++) for (int j = 0; j < 3; j++) scanf("%d", &b[i][j]); transpose(a, ta); transpose(b, tb); printf("Transpose of first matrix:\n"); for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) printf("%4d", ta[i][j]); printf("\n"); } printf("Transpose of second matrix:\n"); for (int i = 0; i < 3; i++) { for (int j = 0; j < 3; j++) printf("%4d", tb[i][j]); printf("\n"); } return 0; } ``` **Sample run** Input: `1 2 3 4 5 6 7 8 9 9 8 7 6 5 4 3 2 1` ```text Enter first matrix (9 values): Enter second matrix (9 values): Transpose of first matrix: 1 4 7 2 5 8 3 6 9 Transpose of second matrix: 9 6 3 8 5 2 7 4 1 ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why does the called function work on the original array? A. A copy is made and returned B. Arrays are global automatically C. The array name gives the address of the first element D. The function uses pointers to a temporary Answer: C. No copy is made; the address is passed. (Key point: Call by address) 2. Which statement performs the transpose? A. t[j][i] = a[i][j] B. t[i][j] = a[j][i] only on the diagonal C. t[i][j] = a[i][j] D. t[i][i] = a[j][j] Answer: A. Rows become columns, so element (i,j) goes to (j,i). (Key point: Transpose rule) 3. In a 2D array parameter, which size is compulsory? A. The row size B. Neither C. The column size D. Both only when initialised Answer: C. The column size is needed to locate a[i][j]. 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