C Review Spring 2015

C ReviewEE319K: Introduction to Embedded Systems

Spring 2015

Outline

Hello World!

Common Data Types

Operators

Control Statements

Functions

Macros

Pointers

Arrays

Struct

Linked List

Hello World

// test.c

#include

/*

this is a block comment

*/

int main(){

printf("Hello World!\n");

}

Output:

Hello World!

Common Data Types

Integer types:

int

unsigned int

int16_t

uint16_t

int32_t

uint32_t

char (int8_t)

unsigned char (uint8_t)

Floating point

types:

float

double

Other types:

bool

void

Declaring and Defining Variables

Every variable needs a type

type variable_name;

Examples:

bool finished; // declaration

uint32_t size = 42; // declaration and definition

Rules for variable names:

Can only consist of alphabets, digits and

underscore

Cannot start with a digit

Declaring and Defining Variables cont.

Conventions:

Use meaningful names (but not too long)

Use average, sum, rather than x, y

Constants are usually all caps

const double PI = 3.14;

Unlike Java, underscore is used to break up

multiple words in variable names

int grade_average; vs. int gradeAverage;

Operators Arithmetic

Operator Description Example

+ Addition a + b

- Subtraction a b

* Multiplication a * b

/ Division b / a

% Modulus b % a

++ Increment (by 1) a++ or ++a

-- Decrement (by 1) a-- or --a

Source: http://www.tutorialspoint.com/ansi_c/c_operator_types.htm

Operators Logical (or Relational)


== Equal a == b

!= Not equal a != b

> Greater than a > b

< Less than a < b

>= Grater than or equal a >= b

Operators Bitwise


& Bitwise AND a & b

| Bitwise OR a | b

^ Bitwise XOR a ^ b

~ Bitwise NOT/Ones

Compliment

~a

Right shift a >> 2


Operators Assignment



= Assignment C = A + B

+= Add AND assignment C += A; // c = c + a

-= Subtract AND

assignment

C -= A; // c = c - a

*= Multiply AND

assignment

C *= A; // c = c * a

/= Divide AND assignment C /= A

%= Modulus AND

assignment

C %= A

Operators Assignment cont.



= 2

&= Bitwise AND assign C &= 2

^= bitwise exclusive OR

and assign

C ^= 2

|= bitwise inclusive OR

and assign

C |= 2

Control Statements - conditional

if statement

if (expression){

statement;

statement;

}

if else statement

if (expression){

statements;

}

else{

statements;

}

Example:

if (temperature > 99.6){

fever = true;

printf(You are having a fever!);

}

Example:

if (temperature > 90)

fever = true;

else

fever = false;

Control Statements - conditional

if else if statement

if (expression){

statements;

}

else if (expression){

statements;

}

else {

}

Example:

if (grade > 90){

printf(You got an A!);

}

else if (grade > 80){

printf(You got an B!);

}

else if (grade > 70){

printf(You got an C!);

}

Control Statements conditional cont.

Switch statement

switch(expression){ // note: expression MUST be

integer type

case some_value: statements; break;

case some_value: statements; break;

default: statements;

}

Example:

char letter_grade;

switch (letter_grade){

case A: gpa += 4; break;

case B: gpa += 3; break;

case C: gpa += 2; break;

defuault: gpa += 0;

}

Control Statements conditional cont.

Selector

(expression)? value_if_true:value_if_false;

Generally used in assignment

Example:

int min = (a > b)? b:a;

Control Statement - looping

for loop

for(initialization; termination; increment){

statements;

}

Example:

for(int i = 0; i < 5; ++i)

printf(%d\n, i);

Output:

0

1

2

3

4

Control Statement looping cont.

while loop

while(expression){

statements;

}

do-while loop

do{

statements;

}while(expression);

Example:

int num = 5;

int factorial = 1;

while(num > 1){

factorial *= num;

--num;

}

Control Statement looping cont.

for(int x = 0; x < 10; ++x)

{

if(x==5)

continue;

printf("%d\n",x);

}

for(int x = 0; x < 10; ++x)

{

if(x==5)

break;

printf("%d\n",x);

}

continue

skips the

statements below

and move on to the

next iteration

break

exits out of the

loop completely

Functions

Similar to subroutines in assembly language

4 important parts: return type, function

name, argument list, and function body

Example:

int sum (int a, int b){

int c = a + b;

return c;

}

IMPORTANT: function needs to be declared

before use

Functions cont.

int main (){

int x = 2, y = 3;

int z = sum(x, y);

printf(%d\n, z);

}

int sum(int a, int b){

return a + b;

}

Compile

Error!!

Functions cont.

int sum(int a, int b);

int main (){

int x = 2, y = 3;

int z = sum(x, y);

printf(%d\n, z);

}

int sum(int a, int b){

return a + b;

}

Output:

5

Scope// example.c

int x; // x is global

int main(){

int y = 4; // y is local

x = 0;

for(int i = 0; i < y; ++i)

// i is only defined inside the for loop

++x;

}

void foo(int a){ // a is local

int y; // this y is different from y in main

int x; // this x is different from global

}

Macros

Use #define to define a label/symbol

Example:

// example.c

#include

#define SW1 0x01

int main(){

int input = data_reg & SW1;

}

Pointers

Pointers are addresses to data in memory

Pointers of any type can be declared with *

Examples:

int *p; // this is a pointer to an integer

char* name_p; // pointer of char

Two new operators:

& : address of

* : dereference

Pointers cont.

// example.c

int main(){

int x = 5;

int *p = &x; // p is address of x

*p = 14; // assign 14 to the location

pointed by p

printf(x = %d\n, x);

}Output:

x = 14;

Arrays

Data structure that stores data sequentially in memory

FIXED LENGTH!!

type array_name[array_size];

All arrays starts with index 0

Example:

int main(){

int grades[10]; // allocates a block of memory for 10

integers

grades[0] = 95; // assign 95 to first element of grades

grades[10] = 100; // segmentation fault!

double prices[] = {1.1, 2.2, 3.3, 4.4, 5.5};

}

Arrays and Pointers

array_name is actually a pointer to the first

element

int x[10], *ptr;

ptr = x; // is the same thing as ptr = &x[0];

Examples of pointer arithmetic

*(ptr + 2) = 14; // x[2] = 14;

ptr++; // ptr now points to x[1];

Struct Struct is a way to group data together

Allows user to define his/her own type

Example:

struct Student{

char name[50];

int id;

}; // make sure to end with semicolon here!

int main(){

struct Student s= {Jenny Chen, 12345};

printf(ID: %d\n, s.id );

// use . to access object member

}

Struct cont.

Pointer to struct, use -> to access elements

Example:

struct Student *s_ptr= &(Student_node){ Jenny

Chen , 12345};

printf(ID: %d\n, s_ptr->id );

// use -> to access member using a pointer

Lined List

Stores a list of data, but not in sequential order

Instead, use pointers to point to the next element

Example:

struct Student_node{

char name[50];

int id;

struct Student_node* next;

};

Jenny Matt Steven

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C Review Spring 2015