Calculator with Decimal, Octal and Hexadecimal Numbers - c

Question

I want to make a calculator that is capable of calculation with decimal numbers and is able to return the decimal values in their respective binary, octal or hexadecimal representation.
So far in the main method the program reads the command line and I can invoke the program by two ways.
The first way would be with 3 values:
"number1" "operator" "number2".
And the second way would be with 4 values:
"wished numeral system for the output" "number1" "operator" "number2".
Where for the wished numeral system output b would stand for for binary, o for octal and h for hexadecimal. In both ways the user should be able to input decimal, octal and hexadecimal numbers for the inputs number1 and number2.
#include "zahlen.h"
#include <stdio.h>
#include "stringTOint.h"
int main(int argc, char *argv[]) {
char o,op,sx[DIGITS+1],sy[DIGITS+1],sz[DIGITS+1];
int x,y,z;
char flag_x,flag_y;
/* 1) Read Commandline */
if (argc != 4 && argc != 5) {
printf("Aufruf: %s -o <x> <op> <y> \n",argv[0]);
return 1;
} else if(argc == 4) {
x = stringTOint(argv[1]);
op = argv[2][0];
y = stringTOint(argv[3]);
} else if(argc == 5) {
o = argv[1][0];
x = stringTOint(argv[2]);
op = argv[3][0];
y = stringTOint(argv[4]);
if(o != 'b' && o != 'o' && o != 'h') {
printf("Wrong Operation\n");
return 1;
}
}
/* 2) Solve the equation */
if(argc==4) {
printf("solve: %s %c %s \n", argv[1], op, argv[3]);
z = solve(x, op, y);
} else if(argc==5) {
printf("solve: %s %c %s \n", argv[2], op, argv[4]);
z = solve(x, op, y);
}
/* 3) Calculate the Representation of the wished Numeral System */
switch(o) {
case 'b':
intTObinaer(x, sx);
intTObinaer(y, sy);
intTObinaer(z, sz);
break;
case 'o':
intTOoctal(x,sx);
intTOoctal(y,sy);
intTOoctal(z,sz);
break;
case 'h':
intTOhexal(x,sx);
intTOhexal(y,sy);
intTOhexal(z,sz);
break;
default:
intTObinaer(x, sx);
intTObinaer(y, sy);
intTObinaer(z, sz);
break;
}
/* 4) Return the results */
printf("\n %s %d\n%c %s %d\n= %s %d\n", sx,x,op,sy,y,sz,z);
return 0;
}
The methods intTObinaer, intTOoctal and intTOhexal only differ by the base with which the decimal number gets divided.
intTObinaer(int i, char str[]) {
unsigned int zahl = i;
int j;
/* Fill Array with zeros */
int x = 0;
for (x; x < DIGITS+1; x++) {
str[x] = '0';
}
/*Calculate the Binary representation of the given Decimal integer */
for (j = DIGITS-1; j > 0; j--) {
/* This base gets changed to 8 or 16 for octal and hexal representation */
str[j] = (char) (zahl % 2) + '0';
zahl = zahl / 2;
if (zahl == 0) {
break;
}
}
/* Set the end of the Array */
str[DIGITS] = '\0';
}
The actual equation gets solved in the solve method, where the right operation for number1 and number2 gets chosen by an switchcase where the different cases can be selected by the char op that the user had input between the two numbers.
#include <stdio.h>
int solve(int x, char op, int y) {
int ergebnis = 0;
switch(op) {
case '+':
ergebnis = x + y;
break;
case '-':
ergebnis = x - y;
break;
case '*':
ergebnis = x * y;
break;
case '/':
ergebnis = x / y;
break;
case '&':
ergebnis = x & y;
break;
case '|':
ergebnis = x | y;
break;
default:
printf("Wrong input\n");
}
return ergebnis;
}
My question now is due to the fact the the user should be able to input different numeral systems(e.g. decimal, octal or hexadecimal) how can I identify the different numeral systems and then transfer them into decimal so that I can calculate the result. After that these decimal Numbers have to be converted back into the desired numeral system that the user wanted.

Answer 1

Looks like you only need to add two lines to do that:
#include "stdlib.h"
#define stringTOint(arg) ((int)strtol(arg,NULL,0))
Or better yet, replace those invocations of stringTOint() with corresponding strtol() invocations (and add the #include, of course).
strtol() uses the same prefixes as for C literals: 0 for octal, 0x for hex, no prefix is decimal.

Answer 2

I would like to suggest another approach to this problem.
Many of the parsing you perform can be performed directly by the sscanf function, the only case is the binary case that needs to be implemented differently.
The implementation follows 3 main step:
Parse the input using the sscanf function (or the ConvCharToBinfor binary values) and store the values in the variables a and b;
Perform the operation and store the result in the res variable;
Print the output result by using the printf parsing (or loop for the binary case).
An implementation would be the following:
#include<stdio.h>
#include<string.h>
typedef struct stack {
unsigned char data[32];
int size;
} stack_t;
int ConvCharToBin(char* input);
int main(int argc, char *argv[]) {
char numSys = 'd', op;
char** param = argv;
int a, b, res;
param++;
//error case
if(argc != 4 && argc != 5) {
//not a valid input
printf("Not a valid input");
return -1;
}
if(argc == 5) {
numSys = param[0][0];
param++;
}
op = param[1][0];
switch(numSys) {
case 'b':
a = ConvCharToBin(param[0]);
b = ConvCharToBin(param[2]);
break;
case 'd':
sscanf(param[0], "%d", &a);
sscanf(param[2], "%d", &b);
break;
case 'h':
sscanf(param[0], "%x", &a);
sscanf(param[2], "%x", &b);
break;
case 'o':
sscanf(param[0], "%o", &a);
sscanf(param[2], "%o", &b);
break;
default:
//no viable number system
return -1;
}
switch(op) {
case '+':
res = a + b;
break;
case '-':
res = a - b;
break;
case '/':
res = a / b;
break;
case '*':
res = a * b;
break;
case '&':
res = a & b;
break;
case '|':
res = a | b;
break;
default:
//no valid operand
printf("invalid operation\n");
return -1;
}
stack_t tmp;
tmp.size = 0;
int i;
switch(numSys) {
case 'b':
while (res) {
if (res & 1) {
tmp.data[tmp.size] = '1';
tmp.size++;
} else {
tmp.data[tmp.size] = '0';
tmp.size++;
}
res >>= 1;
}
for(i = tmp.size - 1; i >= 0; i--) {
printf("%c", tmp.data[i]);
}
printf("\n");
break;
case 'd':
printf("%d\n", res);
break;
case 'h':
printf("%x\n", res);
break;
case 'o':
printf("%o\n", res);
break;
}
return 0;
}
int ConvCharToBin(char* input) {
char* idx;
int res = 0x00000000;
for(idx = input; idx < input + strlen(input); idx++) {
res <<= 1;
if(*idx == '1') {
res |= 0x00000001;
}
}
return res;
}
The sscanf reads formatted data from a string (in you case the argv strings)
This can be parsed using the following:
%d for decimal;
%x for hexadecimal;
%o for octal.
Unfortunately there is no C standard for parsing binary using sscanf, so this is done apart using the stdout.
I would also point out that this implementation has two limitation
Input/output limited to 32 bit unsigned (so from 0 to 4294967295), but with some slight modifications it can be extended;
No error checking for the input values, this can also be easily implemented.