Variables

C includes the following most common types: char, int, long, double and float. A char is always a byte but the size of the other variables is machine dependent. Due to the confusion caused by variable sizes on different machines, in our software we use the types defined in stdint.h. These include the following unsigned types: uint8_t, uint16_t, uint32_t and uint64_t and the following signed types: int8_t, int16_t, int32_t and int64_t, where the numbers are the number of bits the variable holds. These types allow us to have better control over the sizes of our variables. So don’t use a 64 bit variable in a for loop that loops 10 times.

Here you can see how to initialize and set variables using binary, hex and decimal. The // before text is how you make a comment in C.

You may have noticed no mention of strings or booleans, which are common types in several other languages. While a char represents a byte, it also can represent a character, hence the name char. So a string of characters is just an array of chars with a terminating character (\0) as the last element. char[] s = “Hello World” is a away to initialize a char array.

As for booleans we just use a char or uint8_t to represent them. 0 represents false and any other number is true. By convention we use 1 to represent true. So the statement 5 == 5 evaluates to 1 whereas 5 != 5 evaluates to 0.