C

• char - 1 byte - is used to store a single character (ASCII) value

char Temp;    // Variable definition or declaration (letting compiler know we will need it in the future)
Temp = 25;    // Variable initialisation (assigning a value)
extern int my_var // Declaration. It tells the compiler that my_var is defined outside this file

Address of the variable

char a1 = 'A';
&a1                 // Gives you an address - memory location of the variable temp. Type is char* 
printf("%p\n", &a1) // %p - is the special format specifier for pointers

Storage Class of the variable defines:

• Scope of the variable
• Visibility of the variable
• Life time of the variable

static - creates global variable but private to the specific function.

void myFunc(void)
{
  static int count = 0;
  count = count + 1;
  printf("Function was called %d times\n", count);
}

Another use case for static - prevent access to the global variables from another files:

static int internal_global_var; // Won't be accessible outside this file, even with extern

extern - is used to access the global variable, which is defined outside the scope of a file

ASCII

  char a1 = 'A'; // Compiler replaces 'A' with 65 and stores it in a1
  char a2 = 65;  // basically the same as initialising it with 'A'
 
  printf("%c\n", a1); // prints 'A'
  printf("%c\n", a2); // prints also 'A'

• %u - unsigned
• %lf - double
• %f - float
• %le, %e - real number in the scientific representation
• %#x - hexadecimal with a leading 0x
• %s - string

char a1 = 'A'; // Compiler will replace 'A' with 65

If an arithmetic operator has one floating-point operand and one integer operand, however, the integer will be converted to floating point before the operation is done.

1. !=
2. =

• && - AND
• || - OR
• ! - NOT

True is anything but 0, e.g.

uint8_t a = 4;
uint8_t b = 8;
uint8_t c = 0;
 
c = a && b; // c == 1

• & - bitwise AND (usually used to test or clear bits)
• | - bitwise OR (usually used to set bits)
• ~ - bitwise NOT (unary operator, usually used to clear bits)
• ^ - XOR (usually used to toggle bits)

a = ~c; // bitwise unary NOT

• » - a value will be divided by 2 for each right shift
• « - a value will be multiplied by 2 for each left shift

Example clearing the 4th bit with a bitwise shift operator and negation:

data = data &~(1<<4);

Example bit extraction for bits [14:9]. The algorithm:

1. Shift the portion to the right, until it touches the LSB
2. Mask the value to extract only 6 bits [5:0]

data = data >> 9;
data &=63;

WHILE

while(expression) // repeat execution of code inside the loop body until expression evaluates to 0
{
    statemen1;
}