when doing eg "int myvar;" we are:
+ declaraing: saying the variable exists for the code + defining: allocates memory for it
distinction is important, can split up in eg "extern"
Variables rather than addresses within a scope memory location is equivalent to variable: in high level and variables
We can assign a value to a variable by eg:
int a = 10;This does two different things. First it declares the variable \(a\). This assigns part of the memory for the variable. Secondly it defines the value of the memory represented by the variable to \(10\).
These can be split out as follows.
int a;
a = 10;If the variable is declared before it is defined it is an uninitialised variable, and its value is undefined.
In addition to decimal we can also set values using other literals.
int a = 10;
int b = 010;
int c = 0x10;Here \(b\) is octal because of the first \(0\) in the literal. In decimal it is 8. \(c\) is hexidecimal because of the first \(0x\) in the literal. In decimal it is 16.
We can also assign variables from other variables.
int a = 10;
int b = a;The following is valid syntax but unlikely to be what was intended.
int a = 10;
int b;
int c = b = a;lvalue in c identifiable location in memory. not a constant. not a function. not a literal, not a calculation eg (a+b)
left has to be lvalue. right can be lvalue or not int a = 1; // OK. a is an lvalue. doesn’t matter what right is. int b = a; // OK. b is an lvalue. right is also an lvalue, which is ok. (a+b) = 5; // not OK 5 = a; // Not OK left hand side has to be an lvalue. has to be an address we can set result of right hand side to.
CamelCase lowerCamelCase UpperCamelCase
Kebab-Case Upper-Kebab-Case lower-kebab-case
Snake_Case lower_snake_case Upper_Snake_Case
\(\_C\) where C is any capital as variables for C. reserved.