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Variables
"They're something in a program that stores values, this can be a number, a\
character, a pointer a float or arrays of those things."
Variable Type
"the type of a variable is what sort of thing the variable is, what kind of\
value it stores, what operators work on it and the size of it"
Examples
int integer = 34;
char character = 'a';
char * string = "1234";
float floating-point = 12.0;
double doubleFloatingPoint = 111112.0;
int * pointer = &integer;
int array[4] = {0,2,3,4};
Special types of integers
unsigned int unsignedInteger = 4;
short shortInteger = 5;
long longInteger = 1212121212122121212;
uint8_t unsigned8bitInteger = 255;
uint32_t unsigned32bitInteger = 323232323233223232323;
printf("Hello World! %d %c %s\n\a",122,'A',"A String");
"printf is a function a part of stdio(Standard I/O) that allows a program to\
print to serial out(the terminal) it takes a format string and values after that"
Format String
"The format string is what you want printf to print out with, with stuff like\
%d that are placeholders that let you also print out the value of variables you\
supply to printf as arguments"
so in printf("hello world!\n"); "hello world!\n" is the format string
'\n' and '\a' are special characters, '\n' stands for new line and is like
pressing enter. '\a' is the alarm bell and makes a beeping sound
%d is a placeholder for an integer, printed out in decimal(base 10)
%c is a placeholder for a character
%s is a placeholder for a string
for more information look at 'man printf'
What is a function?
"A math function is a when a domain is paired to a co-domain, in programming,\
piece of code that you can run multiple times and does an action"
Function return
"the value a function outputs"
Function argument
"the input to a function"
//How do you run a function
foobar(foo, bar);
also known as a function call;
a function is also an expression
printf("hello world"); is a function call, you're running printf with the
argument "hello world."
"where foobar(int, int) is a function and foo and bar are arguments
that whole piece of code would then evaluate to the output of foobar"
eg.
"if foobar(foo, bar) outputs jia
then foobar(foo, bar); == jia"
Function Definition
"defining a function is when you write down what a function takes as arguments,
what the function returns and what code the function runs"
unsigned int foobar(int foo, int bar) {
int lar = 0;
lar = (foo - bar) * 82 + bar;
return lar;
}
"the above is a function that returns a variable of type 'unsigned int' and
takes two arguments foo and bar that are of type 'int'. it runs the code inside
of the squiggly brackets {}."
Code blocks
"any code inside of an {} are a code block, you can put code blocks inside of
code blocks, that's called nesting code blocks. When you make a new code block
you should indent the code inside of the block"
printf("foobar\n");
i++;
if( i == 0) {
printf("barfoo\n");
j++;
}
"you indent, by putting a tab in front of every line, a tab is a big space"
"When you have a nested code block, you indent another level, or have an extra
tab in front of every line"
foobar
while (barfoo){
foobar
if (baz) {
qux
bazqux
}
foobarbaz
}
Foo Bar Baz Qux
"Foo Bar Baz Qux are placeholder names , they don't mean anything and you can
put your own stuff in place of them."
https://www.ietf.org/rfc/rfc3092.txt for more information
Variable Declarations and Assignments
//When you declaring a variable, you tell the compiler that there is a variable
//named foo of type bar that now exists. You can only use a variable after
//declaring/defining it.
int foo;
//however, right now foo is "uninitialized", meaning there is no value being
//stored in foo, which means you can't use it. Initializing a function is just
//giving it a value.
foo = 0;
//a function that is defined and initialized
bar = 12;
//assigning a value to a variable just changes the value stored by a variable.
foo = 10;
foo = bar;
foo = foobar(12);
foobar(34);
Statements and Expressions
"Expressions evaluate to a value, where as statements do a thing. In c all \
statements are also expressions but you can ignore that"
a + b //is a statement
foobar(34); is a statement because function calls are statements
if (a + b) {} is an if statement
i++; increments i or adds 1 to it.
PRACTICE/REVIEW:
"identify the parts of the below code"
int main(int argc, char * argv[] ) {
if(argc > 1) {
printf("you gave me %d arguments\n",argc);
} else {
printf("you didn't give me any arguments\n");
}
return argc - 1;
}
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