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2) A two dimensional array with each element is a test. In this case the memory of all the test s are already allocated . Also, the memory of the real test s are ready to use without extra preparation.
It is not a multidimensional array - it is array of pointers to int, or array of arrays. To allocate memory for real 2D array you need to use malloc(dim1 * dim2 * sizeof(int)). If some function expects pointer to 2D array, like foo(int * bar[5][6]) and you pass your x, weird things will happen.
In your second example, you explicitly create a pointer to a 2D array: int (*pointer)[100][280]; pointer = &tab1; The semantics are clearer here: *pointer is a 2D array, so you need to access it using (*pointer)[i][j]. Both solutions use the same amount of memory (1 pointer) and will most likely run equally fast.
Easiest Way in Passing A Variable-Length 2D Array. Most clean technique for both C & C++ is: pass 2D array like a 1D array, then use as 2D inside the function.
To access a particular 2D array consider the memory map for an array declaration as shown in code below: 0 1 a[0]0 1 a[1]2 3 To access each element, its sufficient to just pass which array you are interested in as parameters to the function.
You have a "pointer to pointer". That cannot represent a 2D array. The correct declaration of a pointer to a 2D array is // number of elements in one row #define COLS 10 // number of rows #define ROWS 20 int (*array)[COLS]; // mind the parenthesis! That makes array a pointer to array of COLS ints. The type is `int (*)[COLS], btw. but you don't ...
Unlike a plain pointer, this hints about array size, theoretically allowing compiler to warn about passing too-small array and spot obvious out of bounds access. Sadly, it doesn't fix sizeof() and compilers don't seem to use that information yet, so it remains a curiosity.
Similar to this question: 2d array, using calloc in C. I need help initializing a 2D char array that will all be initialized to some value (in this case '0'). I have tried many different methods and I am pulling my hair out. Please let me know what I am doing wrong. This code doesn't work. Thanks!
Secondly, you have a type mismatch; except when it is the operand of the sizeof or unary & operators, or is a string literal being used to initialize another array in a declaration, an expression of type "N-element array of T" will be converted to an expression of type "pointer to T", and the value of the expression will be the address of the ...
The reality is that the 2-D grid you're imagining is actually represented as contiguous, linear memory. So to access a coordinate at index (r,c) you need to start at the base address of the array, then skip to the r-th row by multiplying the row index (r) by the number of columns in each row--again, we're moving in a linear direction.