fscanf

input.c

/*
* make sure the input file is in same folder as the program
* output file will be generated in the same folder
*/

#include <stdio.h>

void readFile(char *fil){
	FILE *fin, *fout; // fin for input, fout for output files
	fin = fopen(fil,"r"); // open input file in read mode
	fout = fopen("output.txt","w"); // open output file in write mode
	int arr[101] = {0}; //initialise an array to store count of each number from 1 - 100
	int tmp;
	while(EOF != fscanf(fin,"%d",&tmp)){ // read number from file until the end of file
		if(tmp>0 && tmp<=100){
			arr[tmp]++;  // increase the count
		}
	}
	fclose(fin); // close input file
	int i;
	for(i=1;i<101;i++){
		fprintf(fout, "%4d - %d\r\n", i,arr[i]);  // write the count of each number to output file
	}
	fclose(fout); //close output file
	printf("Output saved in output.txt\n");
}

int main(int argc, char const *argv[])
{
	readFile("input.txt"); // pass the input filename
	return 0;
}

matrixmultiplication.c

#include<stdio.h> 
#include<conio.h>
void main()
{
	int Matrix A[9][9] , MatrixB[9][9] , Matrixsproduct [9][9] ;
	int n , i , j , k; /* 'i' used for rows and 'j' used for columns */
	int Row1 , Row2 , Column1 , Column2;
	clrscr();
	printf(" Enter the order of Matrix A\n");
	scanf("%d * %d " , &Row1 , &Column1);

	printf(" Enter the order of Matrix B\n");
	scanf("%d * %d " , &Row2 , &Column2);

	if(Column1 == Row2)
	{
		printf(" Enter the elements of Matrix A\n");
		for(i=0 ; i<Row1 ; i++)
		{
			for(j=0 ; j<Column1 ; j++)
			{
				scanf("%d" , &Matrix A[i][j] );
			}
		}

		printf(" Enter the elements of Matrix B\n");
		for(i=0 ; i<Row2 ; i++)
		{
			for(j=0 ; j<Column2 ; j++)
			{
				scanf("%d" , &Matrix B[i][j] );
			}
		}

        /* Product of two Matrices */

		for(i=0 ; i<Row1 ; i++)
		{
			for(j=0 ; j<Column2 ; j++)
			{
				Matrixproduct[i][j] = 0 ;
				for(k=0 ; k<Row2 ; k++)
				{
					Matrixproduct[i][j] = Matrixproduct[i][j] + ( Matrix A[i][k] * Matrix B[k][j] );
				}
			}
		}

		printf(" Product Matrix\n");
		for(i=0 ; i< Row1 ; i++)
		{
			for(j=0 ;j< Column2;j++)
			{
				printf("%d" , Matrixproduct[i][j] );
			}
			printf("\n");
		}
		} /* End of if */
		else
		{
			printf(" Invalid order so Multiplication not possible\n");
		}
}