CODEWITHSUNDEEP
cformatprintf
shino
shino

Reputation: 91

confused by tab (\t) in printf function

Consider this example:

#include <stdio.h>

int main() {
    int fahr, celsius;
    int lower, upper, step;
    
    lower = 0; upper = 300; step = 20;
    
    fahr = lower;
    while (fahr <= upper) {
        celsius = 5 * (fahr - 32) / 9;
        printf("%d\t%d\n", fahr, celsius);
        fahr += step;
    }
    return 0;
}

And get output like this:

0   -17
20  -6
40  4
60  15
80  26
100 37
120 48
140 60
160 71
180 82
200 93
220 104
240 115
260 126
280 137
300 148

since '\t' represent four white spaces, why the output so neat? It seems that the following output format is in accordance with the first one. Thanks for help!

Upvotes: 0

Views: 2634

Answers (2)

Utkarsh Sahu
Utkarsh Sahu

Reputation: 419

/t is itself a character. You cannot mix it up with spaces. It is just like other characters. It too has an ASCII code (09) just like others.

Upvotes: -1

4386427
4386427

Reputation: 44368

since '\t' represent four white spaces ...

Well, that's wrong. Tab (\t) is not four spaces (or any other fixed number of spaces).

Instead it means: Move to the next tab-stop.

The distance between tab-stops are a fixed number. So printing \t will move the cursor to a position that can be written as N * Tab-size.

But notice that tab-size may differ from terminal to terminal. Typically it's either 4 or 8 but it can be other values as well.

Example with tab-size equal 4:

Current position   Next tab-stop (i.e. new position after printing \t)
        0                4
        1                4
        2                4
        3                4
        4                8
        5                8
        6                8
        7                8
        8               12

and so on.

In your case as long as printing fahr requires 3 (or less) characters, celsius will always be printed at position 4.

However, if printing fahr requires 4 characters, you'll see celsius being printed at position 8.

Changing upper to 1200 and step to 200 will give:

0   -17
200 93
400 204
600 315
800 426
1000    537
1200    648

At the first 5 lines celsius is printed at position 4 because printing fahr requires less than 4 characters and consequently the next tab-stop is at position 4.

At the two last lines celsius is printed at position 8 because printing fahr requires 4 characters and consequently the next tab-stop is at position 8.

Upvotes: 3

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