75 lines
3.8 KiB
Markdown
75 lines
3.8 KiB
Markdown
# Compilation Steps
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1. Preprocessing: The preprocessor obeys commands that begin with #, also known as directives
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Commands for the preprocessor are called directives. Directives begin with a pound sign, and they do not end with a semicolon.
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Example:
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```c
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#include <stdio.h>
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```
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2. Compiling. A compiler translates then translates the program into machine instructions.
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3. Linking: The generated objects are combined to create a complete executable.
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The preprocessor is typically integrated with the compiler.
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# Types
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## Strings
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A string literal is characters enclosed in double quotation marks.
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A newline can be inserted using `\n`.
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## Integers
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An integer is a way to store a whole number. In C, integers are signed by default.
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## Floats
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A float is a decimal value. Slower arithmetic and inexact values are both drawbacks of using floats.
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## Variables
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A variable must be declared before it is assigned.
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# Formatting specifiers
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# Standard library
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## Formatting specifiers
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| Specifier | Function |
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| --------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `%d` | Decimal representation: Display a value as a base 10 (hence the decimal) integer. |
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| `%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. |
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| `%e` | Exponential floating point number representation. |
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| `%g` | Either fixed point or exponential representation, whichever has a more compact representation. |
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For number formatting specifiers, the convention is as follows:
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`%-a.bX`
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`%`: Start of the formatting specifier
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`-`: (optional) If included, justify value left in space. Otherwise, justify right in space
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`a`: (optional) If included, the size of the field in characters.
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`.`: Separator between `a` and `b`. Optional if `b` is not specified
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`b`: The number of decimal places to round to
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`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.
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## `printf`
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Used to write a string to stdout with the ability to format variables into the string.
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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.
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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.
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TODO: examples
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## `scanf`
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Read value(s) from stdin.
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`scanf` is to stdin as `printf` is to stdout.
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The format of the input is specified using [formatting specifiers](#Formatting%20specifiers), and all following arguments are pointers pointing to variables to update.
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### Examples
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```c
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// Read a float from standard input into the variable `v`.
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float v;
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// Here, `v` is uninitialized
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scanf("%f", &v);
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printf("You input: %f", v);
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```
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### Behavior
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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.
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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. As `scanf` |