notes/education/software development/ECE1400/C.md

# Compilation Steps

1. Preprocessing: The preprocessor obeys commands that begin with #, also known as directives
Commands for the preprocessor are called directives. Directives begin with a pound sign, and they do not end with a semicolon.

Example:
```c
#include <stdio.h>
```
2. Compiling. A compiler translates then translates the program into machine instructions. 
3. Linking: The generated objects are combined to create a complete executable.

The preprocessor is typically integrated with the compiler.

# Types
## Strings
A string literal is characters enclosed in double quotation marks.

A newline can be inserted using `\n`.

##  Integers
An integer is a way to store a whole number. In C, integers are signed by default.
## Floats
A float is a decimal value. Slower arithmetic and inexact values are both drawbacks of using floats.
## Variables
A variable must be declared before it is assigned.


# Formatting specifiers
# Standard library
## Formatting specifiers
| Specifier | Function                                                                                                                                                    |
| --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `%d`      | Decimal representation: Display a value as a base 10 (hence the decimal) integer.                                                                           |
| `%f`      | Fixed point decimal representation. Specify the number of places to round to by adding a decimal and a number, eg `%.2f` would round to two decimal places. |
| `%e`      | Exponential floating point number representation.                                                                                                           |
| `%g`      | Either fixed point or exponential representation, whichever has a more compact representation.                                                              |
For number formatting specifiers, the convention is as follows:
`%-a.bX`
`%`: Start of the formatting specifier
`-`: (optional) If included, justify value left in space. Otherwise, justify right in space
`a`: (optional) If included, the size of the field in characters.
`.`: Separator between `a` and `b`. Optional if `b` is not specified
`b`: The number of decimal places to round to
`X`: The type of format to use, and the end of the specifier. Use `d` for integer base 10 (decimal) representation, `f` for fixed point decimal, and `e` for exponential notation, and `g` to select between fixed point and exponential, whichever is shorter.
## `printf`
Used to write a string to stdout with the ability to format variables into the string.

Write a string to standard output. `f` indicates that it's a formatting string. The string will not include move the cursor to a newline, append `\n` to the end of the string to do so. 

Printf accepts a variable number of arguments, the first argument is the formatting string, then following arguments are the arguments to be inserted into the string.

TODO: examples
## `scanf`
Read value(s) from stdin.

`scanf` is to stdin as `printf` is to stdout. 

The format of the input is specified using [formatting specifiers](#Formatting%20specifiers), and all following arguments are pointers pointing to variables to update.


### Examples
```c
// Read a float from standard input into the variable `v`.
float v;
// Here, `v` is uninitialized
scanf("%f", &v);

printf("You input: %f", v);
```

### Behavior
The validity of a `scanf` call is not necessarily checked at compile time, and so the number of outputs specified should match the number of inputs. 

For each formatting specifier specified in the string, `scanf` will attempt to locate an appropriate value in the input, skipping whitespace and newlines if necessary until the beginning of a number is reached.

When asked to read an integer, `scanf` searches for one of:
- A digit
- A plus or minus sign
It will continue to read until it reaches a nondigit (whitespace is not skipped in this case, and it is counted as a nondigit). If it doesn't encounter a valid digit first, it will return early. 

When asked to read a float, `scanf` searches for one of:
- A plus sign or minus sign
- A series of digits (possibly containing a decimal point), followed by an exponent (optional). An exponent consists of the letter `e` or `E`