numbers.c

#include <stdio.h>
#include <string.h>

#define OK 0
#define MAX_CHAR 1000


char * translate_number (int x);

int main (int argc, char *argv[])
{
	/* ifp: input file pointer*/
	FILE *ifp;
	/* ofp: output file pointer*/
	FILE *ofp;
	/*number: an integer number to be translated*/
	int number;
	/*output: will hold a pointer of the translated string output*/
	char *output;
	/*the number of command line argument received*/
	int num_of_arguments = argc-1;



	/*this switch case will start the relevant sub program based on the number of argument we received*/
	switch (num_of_arguments) {
		/*2 arguments: the first one will be an input file
		the second one will be the output file*/
		case 2 :
			/*if we were not able to open the input file in read mode*/
			if ((ifp=fopen(argv[1], "r")) == NULL)
				fprintf(stderr ,"Cannot Open file %s\n", argv[1]);
				/*if we were not able to open the output file in write mode*/
			else if ((ofp=fopen(argv[2], "w"))== NULL)
				fprintf(stderr, "Cannot Open file %s\n", argv[2]);
				/*we succeeded to open both files*/
			else
			{
				/*scan numbers from input file to number until reaching EOF*/
				while (fscanf(ifp, "%d", &number) != EOF)
				{
					/*assign the output of translate_number to output*/
					output = translate_number (number);
					/*print the output which contains the translated number to the output file*/
					fprintf(ofp, "%s\n", output);
				}
			}
			/*after we done, close both files*/
			fclose(ifp);
			fclose(ofp);
			break;

			/*we received only one file, this will be the input file, the output will
            be redirected to the standard output*/
		case 1 :
			/*Similar to "case 2", instead writing the output to an output file
			we printing it to the standard output*/
			if ((ifp=fopen(argv[1], "r")) == NULL)
				fprintf(stderr, "Cannot Open file %s\n", argv[1]);
			else
			{
				/*scan numbers from input file to number until reaching EOF*/
				while (fscanf(ifp, "%d", &number) != EOF)
				{
					/*assign the output of translate_number to output*/
					output = translate_number (number);
					/*print the output to the standard output*/
					printf("%s\n", output);
				}
			}
			/*close file*/
			fclose(ifp);
			break;

			/*we didn't received output and input files, the input number will be taken
            directly from the standard input and the output will be redirected to the
            standard output*/
		case 0 : printf("\nUsage:  Hitting Enter will show the result and wait for another input.\n\tCtrl-D will terminate the program.\n\tEntering Characters is not supported!\n\nEnter numbers to be translated:\n");


			/*scan numbers into c while no End-Of-File received*/
			while (scanf("%d", &number) != EOF)
			{
				/*if translate return a 0 value, this means that the entered number is >= 100 and number is < 0*/
				if (*translate_number(number) == '0')
					/*redirect the error message to the system's standard error*/
					fprintf(stderr, "Not Supported Number\n" );
				else
					/*translate didn't retrun '0', then print the string*/
					printf("%s\n", translate_number(number));
			}
			break;

			/*we received more that 2 arguments, print the usage*/
		default : fprintf(stderr, "Not Supported\nUsage:  ./numbers <input file> <output file>\nOr\t./numbers <input file>\nOr\t./numbers\n");
			break;
	}
	return OK;
}


/*translate a digit between 0-99 to english*/
char * translate_number(int x){

	/*output of the String translated number*/
	char output_string[MAX_CHAR];
	/*pointer to output_string*/
	char *ptr;
	/*single digit numbers in english*/
	char *single_digit_number[]={"zero", "one","two", "three", "four", "five", "six", "seven", "eight", "nine", "ten"};
	/*number in english when the second digit of a number is zero*/
	char *second_digit_is_zero[]={"0","", "twenty ", "thirty ", "forty ", "fifty ", "sixty ", "safety ", "eighty ", "ninety "};
	/*the number in english when the first digit is one*/
	char *first_digit_is_one[]={"ten","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen",""};
	ptr = output_string;


	/*if the number between 0-9, return the name of it which located in the number index in single_digit_number array*/
	if (x >= 0 && x < 10)
		return single_digit_number[x];
		/*if number between 9-99 but the first digit is one*/
	else if(x > 9 && x < 100 && x/10 == 1)
		return first_digit_is_one[x%10];
		/*if the number between 9-99 but the second digit is zero*/
	else if (x > 9 && x < 100 && x%10 == 0)
		return second_digit_is_zero[x/10];
		/*if a number that the second digit is not zero and the first digit is not one,
        it result in english as a combination between the both arrays (second_digit_is_zero and single_digit_number)*/
	else if(x > 9 && x < 100 && x%10 != 0 && x/10 !=1)
	{
		/*copy the right string from the first array to the output_string*/
		strcpy (output_string, second_digit_is_zero[x/10]);
		/*concatenate the right string to it from the right array*/
		strcat (output_string, single_digit_number[x%10]);
		/*return a pointer of the ouput_string*/
		return ptr;
	}
	else return second_digit_is_zero[0];
}