C18 cheatsheet

This page is in development, NOT TO BE USED FOR TRAINING!!

FIXME: Check spelling

FIXME: check definition of words used

FIXME: More info C programming is statically typed programming language

See ISO-9899

See Charter

See Wiki

See Books

Example

#include <stdio.h>

// Comment
/* Comment */

// Return highest number in an array
int highestNumber(int numbers[], int size)
{
    int largest = numbers[0];
    for(int i = 1; i < size; i++)
    {
        if(numbers[i] > largest)
        {
            largest = numbers[i];
        }
    }
    return largest;
}

int main() {
    int const size = 7;

    int numbers[size] = {8, 24, 8, 12, 4, 87, 13};

    printf("Highest Number is %d\n", highestNumber(numbers,size));

    return 0;
}

Data types

Defined maximums depends per platform these are examples:

CHAR_BIT    :   8
CHAR_MAX    :   127
CHAR_MIN    :   -128
INT_MAX     :   2147483647
INT_MIN     :   -2147483648
DBL_MIN     :   0.000000
DBL_MAX     :   179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.000000
FLT_MIN     :   0.000000
FLT_MAX     :   340282346638528859811704183484516925440.000000
LONG_MAX    :   9223372036854775807
LONG_MIN    :   -9223372036854775808
SCHAR_MAX   :   127
SCHAR_MIN   :   -128
SHRT_MAX    :   32767
SHRT_MIN    :   -32768
UCHAR_MAX   :   255
UINT_MAX    :   4294967295
ULONG_MAX   :   18446744073709551615
USHRT_MAX   :   65535

See implementation-defined constants

See Reference for datatypes

FIXME: Implement https://www.youtube.com/watch?v=k12BJGSc2Nc&list=PLHTh1InhhwT75gykhs7pqcR_uSiG601oh&index=56

identifiers

identifier is the developer-defined name of a program element.

// Store value '12' in a variable 'something' which is an identifier
int something = 12;
//  ^^^^^^^^^ - identifier

identifiers can be following abcefghijklmnopqrstuvwxyzABCDEFGHCIJKLMNOPQRSTUVWXYZ_0123456789, but they can NOT start with a number.

int 5something = 12;
//  ^ - ILLEGAL! (fixme: why?)

Standard method to write identifiers is to use camel case -> somethingIsNothing (notice that first letter is lowercase)

int someVariable = 12;
//  ^ - Notice lower-case used

Integer

Stores an (integer)[https://en.wikipedia.org/wiki/Integer] which is a number that can be written without a fractional component those are for example 21, 4, 0, and -2048 while 9.75 and √2 are not. ref

// Stores the number '10' in variable 'x'
int x = 10;

integer is represented by int in C18

   int x = 10;
// ^^^ - Interage datatype

Limits for integer value are for example from -2147483648 to 2147483647 on Linux.

Defined in limits.h on unix. ref
Defined in limits.h on windows. ref

int x = 10;
//      ^^ - Value

Float (fixme: summary?)

ref; https://youtu.be/PZRI1IfStY0

FIXME:

"Float is 32-bit number used for storing decimal numbers" nope and nope
there's no guarantee it's 32 bits, and it doesn't store decimals
e.g. 0.1 cannot be represented exactly by a float

Float is … used for storing … from FLT_MIN to FLT_MAX.

These limits are for example 0.000000 to 340282346638528859811704183484516925440.000000

// Stores number 10.5 in variable 'x'
float x = 10.5;
//        ^^^^ decimal

FLT_MIN and FLT_MAX are defined in float.h on unix where using these in limits.h is marked as legacy. (?)

Double (fixme: summary?)

Real floating-point type, usually referred to as a double-precision floating-point type.

Double takes twice as much space compared to float.

FIXME:

a double can store values below 0 e.g. -DBL_MAX or -2
it can also store values outside that range (positive and negative infinity)
and other values that are not a number
and it's not guaranteed to be 64 bits
and I don't know what "not compatible with 32-bit systems" means, but I'm pretty sure it's wrong

These limits are for example 0.000000 to 1797693134862315708145274237317043567980705675258449965989174768031572
6078002853876058955863276687817154045895351438246423432132688946418276
8467546703537516986049910576551282076245490090389328944075868508455133
9423045832369032229481658085593321233482747978262041447231687381771809
19299881250404026184124858368.000000

(FIXME: Rephrase)
Double can represent gigantic numbers as floats, but you lose a ton of precision!

DBL_MAX - 1 will probably be the exact same number as DBL_MAX, because doubles don’t have enough precision to differentiate between even different whole numbers when they’re that size
the biggest double you can store where you can still differentiate between single whole number changes is something like 2^52-1, or 4503599627370495 (assuming IEEE double precision floating points)

// Stores number 10.5 in variable 'x'
double x = 10.5;
//         ^^^^ decimal

Character

Characters are in C represented under the shortcut of ‘‘char’‘ref which stores an integer based on characters that were used to store the value. (fact-check!)

// Store a value '65' in a variable 'foo' on system with ASCII table standard
char x = 'A';

These conversion characters are standardized in an (ASCII table)[https://en.wikipedia.org/wiki/ASCII] depending on the system used for example (IBM mainframe)[https://en.wikipedia.org/wiki/IBM_mainframe] systems using Extended Binary Coded Decimal Interchange Code (EBCDIC)[https://en.wikipedia.org/wiki/EBCDIC] doesn’t recognize the (ASCII tables)[https://en.wikipedia.org/wiki/ASCII] standard.

Note that conversion characters are usually referenced as decimal ASCII characters in a sence of ‘base-10 numbering system’ not to be confused with (Floating-point arithmetic)[https://en.wikipedia.org/wiki/Floating-point_arithmetic]

See Conversion characters

Character array

FIXME: More info requried

char x[] = "char "

Boolean

Booleans were introduced in the header C99 which are used to store a value ‘000000’ for false and ‘000001’ for true assuming bit size limited on 8 bits.

In Standard revision C18 this definition is standardized in stdbool.h library which is expected to be included if boolean data types are to be used in the code.

#include <stdbool.h>

// Store value '000000' in variable 'x'
bool x = false;

long long

FIXME: Add info

Unsigned

FIXME: Fact check!

Unsigned datatypes are used to determine a value to never be negative

unsigned int x = 10;
// FIXME: Add example for long long
unsigned long long x =

Unsigned long long

FIXME: Add info

Print formatted (printf)

Printf is used in C lang to format string and return it as output.

// Output string
printf("%s", "Hello World"); // Returns 'Hello World'

// Output value of variable
char something = "hello";
printf("%d", something); // Returns 'hello'

// Output interage stored in char
char something = 'A';
printf("%i, something); # Returns '65' on a system that is using ASCII standard

Operators

Operators are used to create an expression

// This is binary operator becuase plus has two operands
int x = 5 + 5;
//      ^^^^^ - Expression
//      ^   ^ - Operands
//        ^   - Operator

There are unary, binary and tonary operators

unary = Works on one operand
binary = Works on two operands
tonary = Works on three operands

Aritmetical operators (math)

+ = Addition

// 10 is added by 7 -> value '17' is stored in variable 'x'
int x = 10 + 7;

- = Substraction

// 10 is subtracked by 3 -> value '7' is stored in variable 'x'
int x = 10 - 3;

/ = Division

// 10 is devided by 2 -> value '5' is stored in variable 'x'
int x = 10 / 2;

* = Multiplication

// 10 is multiplied by 2 -> value '20' is stored in variable 'x'
int x = 10 * 2;

% = Modules (reminder of interage devision)

// 10 devided by 3 and whatever is left is set as value of variable 'x' (Stores '1' in variable 'x')
int x = 10 % 3;

Comparison Operators

== = Equal

// If variable 'c' stores a value equal to value '5' -> Return true -> Outputs "Hello World"
if(c == 5)
{
    printf("%s\n", "Hello World");
}

!= = Not Equal

// If variable c stores a value not equal to value '5' -> Return true -> Outputs "Hello World"
if(c != 5)
{
    printf("%s\n", "Hello World");
}

< = Left is smaller then right

// If variable c stores value smaller then value '5' -> Return true -> Outputs "Hello World"
if(c < 5)
{
    printf("%s\n", "Hello World");
}

> = Left is bigger then right

// If variable c stores value bigger then value '5' -> Return true -> Outputs "Hello World"
if(c > 5)
{
    printf("%s\n", "Hello World");
}

<= = Left is smaller or equal to right

// If variable c stores value smaller or equal to value '5' -> Return true -> Outputs "Hello World"
if(c <= 5)
{
    printf("%s\n", "Hello World");
}

>= = Left is bigger or equal to right

// If variable c stores value bigger or equal to value '5' -> Return true -> Outputs "Hello World"
if(c >= 5)
{
    printf("%s\n", "Hello World");
}

Unary minus

FIXME: More info needed

int x = 5;
int y = -x;

// x is 5
// y is -5

Increments

FIXME: Info needed

// `a++;` is same as `a = a + 1;`
a = 5;
b = 5;
b = a++;
//   ^^ - this is evaulated after variable 'a'

// a is 5
// b is 6

Pre-Increments

FIXME: Info needed

b = 5;
a = 5;
b = ++a;
//  ^^ this is evaulated prior to variable 'a'

// b is 6
// a is 6

See Operator precedence

Logic

Expressions

Expressions are any legal combination of code that returns a legal value.

if (true && false || true) ...
//  ^^^^^^^^^^^^^^^^^^^^^ Expression

In C lang expressions are evaulated from left to right

   if(true && false || true) ...
//    ^^^^^^^^^^^^^ - First
//    ^^^^^^^^^^^^^^^^^^^^^ - Second (true AND false is **false** -> **false** OR true is true)

If statements

If statements are used to return an action depending on the logic provided in the expression.

int x = 10;

// If variable 'x' does NOT store a value 10
if(10 != x)
{
    action

// Else If if statement above is false and if variable 'x' does store a value 10
} else if(10 == x)
{
    // In this example this would trigger
    action
// In case both if statements above return false
} else {
    action
};

If statements can also be written in a one line

if (expression) action;

For loops

Run the loop untill expression is false

For loops are usually initiated with expression based on initialization -> comparison -> update

Example of expression for for loop int i = 0; i <= 10; i++ ^^^^^^^^^ initialization ^^^^^^^ Comparison ^^^ Update

Loop with this expression is going to run untill comparison returns false. (for 10 cycles in this example)

for(expression)
{
    action
};

While loop

While expression is true, run the loop

while(i < 20)
{
    // code here
    i++;
};

Functions

FIXME: Needs fact check!

Functions are a collection of code used to perform specific task

#include <stdio.h>

// Output 'Hello Jon aged 67' and return 0

void sayHi(char name[], int age)
//         ^^^^^^^^^^^^^^^^^^^^ - Specifying input
//   ^^^^^ - identifier
//^^ - Prefix?
{
    printf("Hello %s aged %d\n", name, age);
}

int main()
{
    sayHi("Jon", 67);
    return 0;
}

You can use void prefix for a function to set it to not return any information (meaning not storing info in variables?)

void funcname()
{
    // code
}

FIXME: info

Libraries

FIXME: info

Example

Data types

identifiers

Integer

Float (fixme: summary?)

Double (fixme: summary?)

Character

Character array

Boolean

long long

Unsigned

Unsigned long long

Print formatted (printf)

Operators

Aritmetical operators (math)

Comparison Operators

Unary minus

Increments

Pre-Increments

Logic

Expressions

If statements

For loops

While loop

Functions

Libraries

identifiers