How to use an unknown/variable number of variables.

I want to allow the user of my program to load a dataset from a text file. The data will be stored in an array of doubles.

I also want the user to specify how many datasets they wish to load into the program in total and then define the corresponding number of arrays.

My problem is that I don't know how many arrays will be needed in advance (or their size). Does anyone know how to declare an unknown/arbitrary number of variables?

Here is a simplified example of what I want to achieve, where I've used integers instead of arrays. Obviously I want to declare a distinct integer each time inside the loop.

Code:

#include <stdio.h>

int main()
{
    int no_of_integers, i;
    char buffer[100];
    
    printf("Enter the number of integers you want to input\n");
    fgets(buffer, sizeof(buffer), stdin);
    sscanf(buffer, "%d", &no_of_integers);
    
    for (i = 1; i <= no_of_integers; i++){
    
        int integer_i;
        
        printf("Enter integer %d\n", i);
        fgets(buffer, sizeof(buffer), stdin);
        sscanf(buffer, "%d", &integer_i);
        
    }
    
}

(I'm actually not using arrays, but instead matrices as explained in Numerical Recipes in C 2nd Edition, Section 1.2. Although this doesn't change my problem)

Okay, you want to learn about dynamic memory management (in C).

Code:

#include <stdio.h>
#include <stdlib.h>

int main(void) {
	int **matrix, r, c, i;
	puts("Enter rows[tab]columns");
	scanf("%d\t%d", &r, &c);
	matrix = malloc(r*sizeof(int*));
	for (i=0; i<r; i++) matrix[i] = malloc(c*sizeof(int));
	return 0;
}

Dynamic Memory Allocation, Part 1
Beware that discusses C and C++ simultaneously. The C++ stuff is not valid in C.

Chapter 11: Memory Allocation