Integer/Character converter to binary

I wrote this code purely for educational purposes. It also helped

learn more about how exactly things look in memory, so it helped me in that aspect. I'm posting this in order to obtain any suggestions you may have on the code I have right now ( I will likely add more and change it in the future)

Code:

---

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


#define LINE "\n--------------------------------------------------------------------------------\n"


char * int2bin(int number);
void DrawLine();


int main()
{
    char ans = ' ';
    char cinput = ' ';
    int input = 0;
    char * memoryallocated;


    DrawLine();
    printf("  Do you want to translate integers or \ncharacters to binary? [i/c]\n\n");
    scanf("%1c", &ans);
    DrawLine();


    if (toupper(ans) == 'I') {
        printf("Type in a number and press enter to convert a number to binary! \n");
        DrawLine();
    do
    {
        fflush(stdin);
        scanf("%d", &input );
        DrawLine();
        memoryallocated = int2bin(input);
        DrawLine();
        if (memoryallocated != NULL) { free(memoryallocated); } else {exit(1); break;}
    } while (1);
    } else if (toupper(ans) == 'C') {
        printf("Type in a character and press enter to convert it to binary! \n");
        DrawLine();
        do {
        fflush(stdin);
        scanf("%1c", &cinput );
        DrawLine();
        memoryallocated = int2bin((int)cinput);
        DrawLine();
        if (memoryallocated != NULL) { free(memoryallocated); } else {exit(1); break;}
        } while(1);
    }


    return 1;
}


char * int2bin(int number)
{
    char * StartOfBin;
    char * BinPtr;
    size_t MemAmount;
    int bitnum = 4;
    int charbyteamount = 1;
    int PlaceValue;
    int n = 0;
    int ctr = 0;
    int * tempmem = (int *)malloc(1 * sizeof(int));
    *(tempmem + 0) = number;


    do
    {
        if (number <= (pow(2, bitnum) - 1)) {StartOfBin = (char*)malloc(MemAmount = (sizeof(char)* ((4 * charbyteamount) + 1))); break; }
        bitnum *= 2;
        charbyteamount *= 2;
    } while (1);


    BinPtr = StartOfBin;


    if ( StartOfBin != NULL ) {
        for(; n < (MemAmount - 1); n++) { *(BinPtr + n) = '0'; }
        *(BinPtr + (n)) = '\0';
    } else return NULL;


    BinPtr = StartOfBin;
    PlaceValue = (pow(2,n)/2);


    do
    {
        if (number >= PlaceValue) {
                *(BinPtr + 0) = 0b00110001; // '1'
                number -= PlaceValue;
                PlaceValue /= 2;
                BinPtr++;
                ctr++;
                } else {
                PlaceValue /= 2;
                BinPtr++;
                ctr++;
                }
    } while (ctr < n);


    printf("%d = %s \n", *(tempmem+0), StartOfBin);
    free(tempmem);


    return StartOfBin;
}


void DrawLine() { printf("%s", LINE); }

---

It's not looking too bad, but here are some improvements.

Indentation (see SourceForge.net: Indentation - cpwiki) could be better in places.
In particular, code following an opening brace is a no-no.

> int * tempmem = (int *)malloc(1 * sizeof(int));
Do not cast malloc in a C program.
If you get a warning about "cannot convert void*", then you need to stop using a C++ compiler to compile C code (perhaps change prog.cpp to prog.c).

> *(BinPtr + 0) = 0b00110001; // '1'
Not all compilers support binary constants.
You may as well have said *(BinPtr + 0) = '1';
and saved you the trouble of writing a comment.

> fflush(stdin);
NO.
SourceForge.net: Fflush - cpwiki

> int main .... return 1;
The successful return from main should be return 0; or return EXIT_SUCCESS;

> if (toupper(ans) == 'I')
Create a pair of functions to make main tidier.
Say

Code:

---

if (toupper(ans) == 'I') {
  doIntegerConversion();
} else if (toupper(ans) == 'C') {
  doCharacterConversion();
}

---

and move the respective blocks of code into the separate functions.

Hello again, in response to Salem's post I have made several changes...

1) It is now possible to break out of the loop to exit and change which conversion you are using.

2) I removed the casting of malloc()

3) I replaced fflush(stdin) with getchar(). ( I still needed a way to "clean" the buffer, and I knew a call to getchar() could work )

4) Replaced the 0b00110001 binary number with plain old '1' in single quotes.

5) Moved the 2 conversions into different functions, as Salem suggested.

6) Improved and re-checked indentation

That's all the updates I made to the program now. Feel free to post anything I missed or made a mistake on in the new code.

Code:

---

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

#define LINE "\n--------------------------------------------------------------------------------\n"

char * int2bin(int number);
void IntegerToBinaryConversion();
void CharacterToBinaryConversion();
void DrawLine();

int main()
{
    char ans = ' ';

    DrawLine();

    do {
            printf("  Do you want to translate integers or \ncharacters to binary? (press e to exit) [i/c/e]\n\n");
            scanf("%1c", &ans);
            DrawLine();

            switch(toupper(ans))
            {
            case 'C' :
                printf("Type in a character and press enter to convert it to binary! \n");
                DrawLine();
                CharacterToBinaryConversion();
                break;
            case 'I' :
                printf("Type in a number and press enter to convert a number to binary! \n");
                DrawLine();
                IntegerToBinaryConversion();
                break;
            case 'E' : break;
            }
        getchar();
       
    } while (toupper(ans) != 'E');

    return 0;
}

char * int2bin(int number)
{
    char * StartOfBin;
    char * BinPtr;
    size_t MemAmount;
    int bitnum = 4;
    int charbyteamount = 1;
    int PlaceValue;
    int n = 0;
    int ctr = 0;
    int * tempmem = malloc(1 * sizeof(int));
    *(tempmem + 0) = number;

    do
    {
        if (number <= (pow(2, bitnum) - 1)) {StartOfBin = malloc(MemAmount = (sizeof(char)* ((4 * charbyteamount) + 1))); break; }
        bitnum *= 2;
        charbyteamount *= 2;

    } while (1);

    BinPtr = StartOfBin;

    if ( StartOfBin != NULL )
    {
        for(; n < (MemAmount - 1); n++) { *(BinPtr + n) = '0'; }
        *(BinPtr + (n)) = '\0';

    } else return NULL;

    BinPtr = StartOfBin;
    PlaceValue = (pow(2,n)/2);

    do
    {
        if (number >= PlaceValue)
        {
            *(BinPtr + 0) = '1';
            number -= PlaceValue;
            PlaceValue /= 2;
            BinPtr++;
            ctr++;

        } else {
            PlaceValue /= 2;
            BinPtr++;
            ctr++;

        }
    } while (ctr < n);

    printf("%d = %s \n", *(tempmem+0), StartOfBin);
    free(tempmem);

    return StartOfBin;
}

void DrawLine() { printf("%s", LINE); }

void IntegerToBinaryConversion()
{
    int input = 0;

    getchar();
    scanf("%d", &input );

    DrawLine();
    char * memoryallocated = int2bin(input);
    DrawLine();

    if (memoryallocated != NULL) { free(memoryallocated); } else {exit(1);}

    return;
}

void CharacterToBinaryConversion()
{
    char cinput = ' ';

    getchar();
    scanf("%1c", &cinput );

    DrawLine();
    char * memoryallocated = int2bin((int)cinput);
    DrawLine();

    if (memoryallocated != NULL) { free(memoryallocated); } else {exit(1);}

    return;
}

---

You can make inttobin a lot tighter.

Why not create another function that is responsible for receiving user input? This way you can keep the code used to clear the input buffer all in one place.

For instance, have a function that calls "fgets()", and use "sscanf()" to extract the information you need, which you can return to the calling function.

Use the return value of "sscanf()" to determine if items were successfully read from your string.

Also, "fgets()" stores the newline as part of the string, if there is room for it. Based on this, you can do a simple check as follows - if the entered string ends in a newline, you know the entire line entered by the user has been read, therefore there is no need to clear the input buffer. If there is *no* newline in that string, then you know that there are extra characters floating around the input buffer, which can be eaten up by a simple loop using "getchar()".

*(BinPtr + n) etc can be replaced with BinPtr[n] same with anywhere else you use that form of syntax.

Don't use pow where a bit-shift can be used instead. That's using a sledgehammer to crack a nut.

when l compiled it, it gave me errors: gcc -Wall -Werror -O -o program program.c
/tmp/ccbTt6Ih.o: In function `int2bin':
ggg.c: (.text+0x4f): undefined reference to `pow'
ggg.c: (.text+0xc6): undefined reference to `pow'
collect2: ld returned 1 exit status
why does it give me these errors? how can l fix them?

You may need to link to the math library, e.g., by using the -lm option.