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#1
December 12th, 2012, 11:51 PM
 Astrodude
Registered User

Join Date: Oct 2012
Posts: 22
Time spent in forums: 3 h 57 m 34 sec
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Base conversion

I'm trying to write a program with a function that can convert an integer in any base in the range of 2 to 16 to an integer in any base in the range of 2 to 16.

I know how to convert to base 10 from any of those bases, but I don't know how to then convert to bases larger than 10 with using a ton of if statements. Recall that mod will return a result in base 10 so I would have to convert '10' to 'A' 6 times in if statements. Is there a shorter way to do it?

This is what I have so far:
Code:
```  #define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define MAXBUF 64
int conversions(char s[], int sb, char d[], int db);
void main()
{
char s[MAXBUF+1],d[MAXBUF+1]; // source, destination value
//        (as char string)
int sb,db; // source, destination base
int decval; // calculated decimal value
char buf[MAXBUF+10]; // temp buffer
char *p; // pointer to string
printf("Enter src value, src base, dst base: ");
gets(buf);
p=strtok(buf, " ,");
while (stricmp(p,"END"))
{
strcpy(s,p);
p=strtok(NULL," ,"); // or sb=atoi(strtok(NULL," ,"))
sb=atoi(p);
p=strtok(NULL," ,"); // or db=atoi(strtok(NULL," ,"))
db=atoi(p);
decval=conversions(s,sb,d,db);
printf("%s|%d = %d|10 = %s|%d\n",s,sb,decval,d,db);
printf("Enter source value, source base, dest base: ");
gets(buf);
p=strtok(buf," ,");
}
}
// your actual conversions() function goes here
int conversions(char s[], int sb, char d[], int db){

int sourcevalues[],base10[];
int size;
int i,j;

size=strlen(s[]);
while(s[0]=' ')
{
size=strlen(s);
for (int i=0; i<size; i++)
{
s[i]=s[i+1];
}
size=strlen(s[]);
}

for(i=0;i<size,i++){
if(s[i]>=sb){
d[]={'E','R','R','O','R'};
return -1;

elseif((s[i]=='0')||(s[i]=='1')||(s[i]=='2')||(s[i]=='3')||(s[i]=='4')||(s[i]=='5')||(s[i]=='6')||(s[i]=='7')||(s[i]=='8')||(s[i]=='9')){
sourcevalues[i]=s[i]-'0';
}
elseif((s[i]=='A')||(s[i]=='B')||(s[i]=='C')||(s[i]=='D')||(s[i]=='E')||(s[i]=='F')){
sourcevalues[i]=s[i]-'55';
}
}
}
for(j=0;j<size;j++){
base10[j]=sourcevalues[j]*(pow(sb,(size-j-1)));
}
int k;
k=base10[0];
for(j=1;j<size;j++){
k=k+s[j];	//k is the number converted to base 10;
}
int m; //another for loop for base conversion
for(
```

#2
December 13th, 2012, 12:55 AM
 dwise1_aol
Contributing User

Join Date: Jan 2003
Location: USA
Posts: 6,142
Time spent in forums: 2 Months 2 Weeks 4 Days 12 m 13 sec
Reputation Power: 1974
I didn't try to read your code, though posting it was definitely the right thing to do.

The procedure for converting from decimal to any other number base is the same regardless of what that number base is: building from the least significant digit, divide by the base, take the remainder as the digit, rinse and repeat until the quotient is zero.

The only question would be how to handle that remainder for a number base greater than 10 and for digits greater than 9. Again, if <= 9, then add '0', else subtract 10 and add 'A'.

Of course, that will only take you up to about base 36. For something like Base64 (an actual base that's used to transmit binary data as ASCII characters), read the specification.

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