printf

How it's called

printf("message") // For just printing a string
 
printf("A %s formatted message!", "fancy") // For printing messages with data in between. 
//For every format specifier, add another argument to the function call

Control sequences

Control Sequence	What it does
\n	New line
\t	Tab (indent)
\\	Represents \ (since it’s used in control sequences)
%%	Represents % (since it’s used in format specifiers)

Remember: Unlike other languages, c will NOT create a new line for you! Use \n always!

Formatting outputs

The %‘s are Format Specifier’s and are used to format strings with data from variables concatenated in between in a fancy way. Here are a few common ones

Format Specifier	Used to format…
%d	Integers (Decimal)
%s	Strings
%f	Floats
%p	Pointers (as hexadecimal)
%ld	Longs (“Long Decimals”)
%lf	Doubles (“Long Floats”)

Decimal points and whole number points

• It rounds
• it’s weird
• strange times.

Remember that pi question in week 1 lecture notes? Well there is this convenient notation to only print out x number of characters of a variable.

float x = 1234.5678;
printf("Prints 1234.57: %2.2f\n", x); // Rounds; Prints 2 numbers before the decimal, and 2 numbers after the decimal.  
// Since a has 4 numbers before the decimal, it'll print out all 4 numbers. 
x = 1.5555;
printf("Prints 1.56: %3.2f\n",x); 
 
// Lastly, for ints, you can decide how many numbers it prints
int y = 4; 
printf("%4d\n", y); // Prints 4 with 3 spaces before it.
 
y = 24;
printf("%04d", y); // Prints 24 with 2 0's before it.

todo play w/ this more. i wanna print 0’s before and after the number.

let a.b be the precision.

1. ‘a’ is the number of characters printed. If there are less characters than a is, it’ll add spaces at the front. If it’s too small, it won’t actually do anything (it doesn’t cut off numbers)
2. b is the number of decimals. It rounds at the decimal or whole number we end at.
   1. So 12.567 with the format of 5.0 would be 13
   2. 12.567 with 2.3 would be 12.567

The same thing but for integers

In a.b, a has basically the same behavior (it’ll ensure there are a characters. If there are not enough numbers, add spaces at the start until we hit a. If there’s too many numbers, we still print them all). However b is more similar to a with integers. No rounding happens though. Instead, if a < numbers, then nothing happens. If a > numbers, then it will print extra 0’s

So 1234 with 8.5 would be 01234

printf("8.5%d", 1234); // Prints what i said abv

And 98 with 3.1 would be 98 And lastly 123 with 0.4 will be 0123