conversion table from feet and inches to cm - c

Question

I need to write a program which prints the conversion table from feet and inches to centimetres. The numbers printed in row i (counting from zero), column j (counting from zero) of the table should be the cm equivalent of i feet and j inches. i should go from 0 to 7, and j from 0 to 11. Each column should be five characters wide, and the cm figures should be rounded to the nearest integer.
The example of required output is given below:
0 3 5 8 10 13
30 33 36 38 41
61 64 66 69 71
91 94 97 99 102
The code I have prints only one row of inches and column of feet but I don't know how to make into table without producing lots of irrelevant repetitions.
The code is:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main()
{
int i,j;
int cm,p;
for (i=0; i<= 11; i++) {
cm =round(i * 2.54);
printf ("%5d",cm);
}
for (j=0; j<=7; j++) {
p =round(j* 12.0 * 2.54);
printf ("%5d\n",p);
}
return 0;
}
This produces:
0 3 5 8 10 13 15 18 20 23 25 28 0
30
61
91
122
152
183
213
What am I doing wrong?

Answer 1

You have one loop after the other. What you need to do is run through the inches loop every iteration of your feet loop. What you get is nested loops:
#include <stdio.h>
int main()
{
for (int feet = 0; feet <= 7; ++feet) {
for (int inches = 0; inches < 12; ++inches) {
int microns = (feet * 12 + inches) * 25400;
int rounded_cm = (microns + 5000) / 10000;
printf("%5d", rounded_cm);
}
puts("");
}
}
I've made some other changes in my version; you're encouraged to study it and understand why it does what it does (read the man page for puts(), for example). Don't just copy it and hand it in - it will be obvious it isn't your code.
An alternative approach is to use a single loop (in inches), and insert a newline when we reach the 11th inch in each foot:
#include <stdio.h>
int main()
{
for (int i = 0; i < 96; ++i) {
printf("%4d%s",
(i * 25400 + 5000) / 10000,
i%12==11 ? "\n" : " ");
}
}
(You'll want to give meaningful names to your constants; the above is written in a "code-golf" style).
Whatever you do, don't be tempted to avoid multiplying by instead adding 2.54 repeatedly in the loop. Floating-point numbers are not exact, and addition will accumulate the error.

Answer 2

OP needs to put the "inches" loop inside the "foot" loop as well answered by others. #Toby Speight #VHS
Code could do its "round to nearest" via the printf() statement by using "%5.0f" to control the output width and rounding.
Let code use foot/inch instead of i/j #KevinDTimm for clarity.
#include <stdio.h>
#define INCH_PER_FOOT 12
#define CM_PER_INCH 2.54
int main(void) {
// go from 0 to 7, and ...
for (int foot = 0; foot <= 7; foot++) {
// from 0 to 11
// for (int inch = 0; inch < INCH_PER_FOOT; inch++) { is more idiomatic
for (int inch = 0; inch <= 11; inch++) {
printf("%5.0f", (foot * INCH_PER_FOOT + inch) * CM_PER_INCH);
}
puts("");
}
}
Output
0 3 5 8 10 13 15 18 20 23 25 28
...
213 216 218 221 224 226 229 231 234 236 239 241

Answer 3

You are running your loops backwards. First you need to run through feet and then through inches. But you are having it the other way round. Check the following snipped and compare it with your code and try to understand what's wrong.
#include <stdio.h>
#include <stdlib.h>
#include <math.h> // for rounding of a number
int main()
{
int i,j;
int cm,p;
for(i=0; i<=7;i++) {
for(j=0;j<=11;j++) {
cm = round(i*30.48 + j*2.54);
printf ("%5d",cm);
}
printf("\n");
}
return 0;
}