C Language Quick Reference

7/31/2019 C Language Quick Reference

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C Programming Language

Quick Reference

V1.3

June 2009Information contained in this publication regarding device applications and the like is intended through suggestion only and may besuperseded by updates. It is your responsibility to ensure that your application meets with your specifications. No representation or

warranty is given and no liability is assumed by Cytron Technologies Incorporated with respect to the accuracy or use of such information

or infringement of patents or other intellectual property rights arising from such use or otherwise. Use of Cytron Technologiess products

as critical components in life support systems is not authorized except with express written approval by Cytron Technologies. No licenses

are conveyed, implicitly or otherwise, under any intellectual property rights.


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ROBOT . HEAD to TOEQuick Reference C Programming Language

Created by Cytron Technologies Sdn. Bhd. All Rights Reserved

Index

1. Introduction 1

2. Standard Method to Start 1

a. C Comments 1

b. Include Header File 2

c. Configuration Bits 2

d. Include Libraries, Functions declaration and Global variables 2

e. Function Name 2

f. Function Body 2

3. Radix Format 3

4. Identifiers, Variables and Keywords 3

a. Identifiers 3

b. Variable 4

c. Keywords 4

d. Data Type 5

e. Declaring Variable 6

f. Array 6

g. String 7

5. Operators 9

a. Arithmetic Operators 9

b. Assignment Operators 9

c. Relational Operators 10

d. Logical Operators 10

e. Bitwise Operators 10

f. Shift Operators 10

g. Memory Addressing Operators 11


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Created by Cytron Technologies Sdn. Bhd. All Rights Reserved

h. Other Operators 11

i. Operator Precedence 12

6. Statements 13

a. Expression Statements 13

b. Compound Statements 13

c. Control Statements 14

i. if Statement 15

ii. switch Statement 16

iii. for Statement 19

iv. while Statement 20

v. do-while Statement 21

vi. break Statement 22

vii. continue Statement 23

7. Function 24

8. Creating Project using MPLAB + HI-TECH C PRO Compiler 27

9. Starting a PIC Program 36


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Created by Cytron Technologies Sdn. Bhd. All Rights Reserved 1

1. Introduction

This reference guide is intended to quickly introduce user to C language syntax with the aim

to easily start programming microcontroller (PIC) during code development.

1st

question, Why C language? Because C offers unmatched power and flexibility in

programming microcontrollers.

2. Standard Method to Start

There is no 100% correct ways to write c program, anyway there are guide lines to follow.

Let see what a C file contains.

a. C Comments/* Put your comments here. This is actually the format of C comments. It may takes

multiple lines, as long as it is end with */

OR

// Put your comments after //, this only allow one line.

// If you need multiple lines you will need // in front of each line.

// This is C++ format of putting comments.

Prepared byCytron Technologies Sdn. Bhd.

19, Jalan Kebudayaan 1A,

Taman Universiti,

81300 Skudai,

Johor, Malaysia.

Tel: +607-521 3178

Fax: +607-521 1861

URL: www.cytron.com.my

Email: [email protected]

[email protected]

a. Comments

b. Include header

file

c. Configuration

bits

d. Include libraries,

function declaration,lobal variable

e. Function name

f. Function

body

End of block

Begin of

Block


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b. Include Header File#include is to called the proper header file. It enables the compiler to

include file which define standard keyword for PIC based on model. It also includes

certain functions contained in the external file htc.h.

As the file placed before the program proper, it is called a header file (with the fileextension .h).

c. Configuration BitsA macro that writes a value into the special register that controls the core executing

operations of the microcontroller. It start with two _ and followed with

CONFIG(configuration bits);

If the configuration bits are not specified correctly, the PIC MCUs might not run the

application code properly

d. Include Libraries, Functions declaration and Global variablesThis section can be leaved blank depend on program writer. However, if there is

necessary to include other header file, libraries, to declare functions prototype and global

variables, it should be placed here.

e. Function NameAll C programs are written in terms offunctions. It is the basic building block in C

programming. C program must have at least the function main( ). The void means the

main( ) function doesn't return any value when it exit (finish running)..

f. Function BodyEvery function, including main( ), must have a body enclosed in braces { }.The function

body (also called block) can be of any size. The curly braces are to signify the block of

codes belonging to main( ). Do take note that there MUST NOT be a semicolon after the

closing brace.


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3. Radix Format

Radix format is the way a value is being presented in C language

There are four methods to present value:

Radix Format Comments

Binary 0bnumberor0BnumberMPASM binary is in format Bnumber.

Octal 0numberor\number Inadvertently putting a 0 in front of a decimal

number will convert it to octal for the compiler,

potentially resulting in errors that are very hard to

find.

Decimal number MPASM default is hexadecimal

Hexadecimal 0xnumberor0XnumberMPASM also enables Xnumber.

4. Identifiers, Variables and Keywords

a. Identifiers

Identifiers are simply names or labels given to program elements such as variables, functions,

arrays.

A valid identifier has the rules of:

Remember! Is case sensitive, Temp not the same as temp.

I d e n t i f i e rFirst Character

_ (underscore)A to Za to z

Remaining Characters_ (underscore)

A to Za to z0 to 9


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b. VariableA variable is a valid identifier that represents one or more memory locations used to hold

program data. It must be declared before uses. Data type must be assigned to a variable.

c. KeywordsKeywords also called reserved words, have standard, predefined meanings and must be used

only for their intended purpose.

asm

class

do

far

huge

long

protected

sizeof

typedef

volatile

auto

const

double

float

if

near

public

static

union

while

break

continue

else

for

inline

new

register

struct

unsigned

case

default

enum

friend

int

operator

return

switch

virtual

char

delete

extern

goto

interrupt

private

short

this

void


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d. Data TypeData Type is type assigned to variable to determine the size and how the variable being

interpreted.

Fundamental Type

Type Description Bitschar single character 8

int integer 16

float single precision floating point number 32

double double precision floating point number 64

Modified Integer Types

Qualifiers: unsigned, signed, short and long

Qualified Type Min Max Bits

unsigned char 0 255 8char, signed char -128 127 8

unsigned short int 0 65535 16

short int, signed short int -32768 32767 16

unsigned int 0 65535 16

int, signed int -32768 32767 16

unsigned long int 0 232-1 32

long int, signed long int -231 231-1 32

unsigned long long int 0 264-1 64

long long int, signed long long int -263 263-1 64

Modified Floating Point Types

Qualified TypeAbsolute

MinAbsolute

Max Bits

float ~10-44.85 ~1038.53 32

double1 ~10-44.85 ~1038.53 32

long double ~10-323.3

~10308.3

641. HI-TECH C PRO is either using IEEE-754 Format or modified (Truncated) 24-bit Format


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e. Declaring Variable

Standard Syntax

type identifier1, identifier2,.., identifiern;

Other methodOne declaration on a line

type identifier;

One declaration on a line with an initial value

type identifier InitialValue;

Multiple declarations of same type of a line

type identifier1, identifier2, identifier3;

Multiple declarations of same type of a line with initial values

type identifier1= Value1, identifier2 = Value2;

Example:unsigned int x;

unsignedy = 12;int a, b, c;long int myVar = 0x12345678;long z;char first = 'a', second, third = 'c';

float big_number = 6.02e+23;

f. ArrayArrays are variables that can store many items of the same data type. The individual items

known as elements, are stored sequentially and are uniquely identified by the array index

(sometimes called a subscript). The index is zero based.

Standard Syntax

type arrayName[size];

size refer to the number of elements and it must be a constant integer.

Declaration with initialization

type arrayName[size] = {item1, . , itemn};

The items must all match the type of the array.

Example:int a[5] = {10, 20, 30, 40, 50};


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Using Array:

Standard Syntax

arrayName[index]

index may be a variable or a constant

The first element in the array has an index of 0

Example1:int i, a[10]; //An array that can hold 10 integers

for(i = 0; i < 10; i++)

{a[i] = 0; //Initialize all array elements to 0

}

a[4] = 42; //Set fifth element to 42

Example2:unsigned char count[5] = {1,2,3,4,5};

element Value

count[0] 1

count[1] 2

count[2] 3

count[3] 4

count[4] 5

g. StringStrings are arrays of char whose last element is a null character \0 with an ASCII of 0. C has

no native string data type, so strings must always be treated as character arrays.

Strings:

- Are enclosed in double quotes string.- Are terminated by a null character \0.- Must be manipulated as arrays of characters (treated element by element).- May be initialized with a string literal.

Declaration with initializationchar arrayName[] = Cytron Technologies;

Element size is not required.

Size automatically determined by length of string.

NULL character \0 is automatically appended.

Example:char str1[] = Cytron"; // 7 chars Cytron\0"

//Alternative string declaration size requiredchar str3[4] = {'P', 'I', 'C', '\0'};


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Following show the ASCII table:


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5. Operators

Most C Compiler recognizes following operators:

- Arithmetic Operators- Assignment Operators- Relational Operators- Logical Operators

- Bitwise Operators- Shift Operators- Memory Addressing Operators- Other Operators

a. Arithmetic Operators

Operator Operation Example Product Remarks

* Multiplication x * y Product of x and y Binary

/ division x / y Quotient of x and y Binary

% Modulo x % yRemainder of x divided byy Binary

+ Addition x + y Sum of x and y Binary- Subtraction x - y Difference of x and y Binary

+ Positive + x Value of x Unary

- Negative - y Negative value of y Unary

++ Increment ++ x increase x by 1 Unary

-- Decrement -- x decrease x by 1 Unary

b. Assignment Operators

Operator Operation Example Result

= Assignment x = y Assign x the value of y

+= Compound Assignment x += y x = x + y-= Compound Assignment x -= y x = x - y

*= Compound Assignment x *= y x = x * y

/= Compound Assignment x /= y x = x / y

%= Compound Assignment x %= y x = x % y

&= Compound Assignment x &= y x = x & y

^= Compound Assignment x ^= y x = x ^ y

|= Compound Assignment x |= y x = x | y

> y


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c. Relational Operators

Operator Operation Example Result (FASLE = 0, TRUE0)

< Less than x < y 1 if x less than y, else 0

y 1 if x greater than y, else 0

>= Greater than or equalto x >= y 1 is x greater than or equal to y, else0

== Equal to x == y 1 is x equal to y, else 0

!= Not equal to x != y 1 is x not equal to y, else 0

d. Logical Operators

Operator Operation Example Result (FASLE = 0, TRUE0)

&& Logical AND x && y 1 if both x 0 and y 0, else 0

|| Logical OR x || y 1 if both x = 0 and y = 0, else 1

! Logical NOT !x 1 if x = 0, else 0

e. Bitwise Operators

The operation is carried out on each bit of the first operand with each corresponding bit of the

second operand.

Operator Operation Example Result (for each bit position)

& Bitwise AND x & y1 if 1 in both x and y

0, if 0 is x or y or both

| Bitwise OR x | y1, if 1 in x or y or both

0, if 0 in both x and y^ Bitwise XOR x ^ y

1, is 1 in x or y but not both

0, if 0 or 1 in both x and y

~ Bitwise NOT ~x1, if 0 in x

0, if 1 in x

f. Shift Operators


Shift Right x >> y Shift x by y bits to the right


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g. Memory Addressing Operators

Operator Operation Example Result& Address of &x Pointer to x* Indirection *p The object of function that p points to[ ] Subscripting x[y]

The y

th

element of array x. Struct/Union Member x.y

The member named y in the structureor union x

->Struct/Union Memberby Reference

p->yThe member named y in the structureor union that p points to

h. Other Operators


( ) Function call foo(x)Passes control to the function withthe specified arguments

sizeof Size of an object ortype in bytes sizeof x the number of bytes x occupies inmemory

(type) Explicit type cast (short) xConverts the value of c to thespecified type

?:Conditionalexpression

x ? y : zThe value of y if x is true, else valueof z

,Sequentialevaluation

x, yEvaluates x then y, else result isvalue of y


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i. Operator Precedence

Which operator will be evaluated first?

Operator Description Associativity

( ) Parenthesized Expression

Left-to-Right[ ] Array Subscript

. Structure Member

-> Structure Pointer

+ - Unary + and - (Positive and Negative Signs)

Right-to-Left

++ -- Increment and Decrement

! ~ Logical NOT and Bitwise Complement

* Deference (Pointer)

& Address of

sizeof Size of Expression or Type

(type) Explicit Typecast

* / % Multiply, Divide, and Modulus

Left-to-Right

+ - Add and Subtract

> Shift Left and Shift Right< >= Greater Than and Greater Than or Equal To

== != Equal To and Not Equal to

& Bitwise AND

^ Bitwise XOR

| Bitwise OR

&& Logical AND

|| Logical OR

? : Conditional Operator

Right-to-Left

= Assignment+= -= Addition and Subtraction Assignments

/= *= Division and Multiplication Assignments

%= Modules Assignment

= Shift Left and Shift Right Assignments

&= |= Bitwise AND and OR Assignments

^= Bitwise XOR Assignments

, Comma Operator Left-to-Right


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6. Statements

Statements can be roughly divided into:

- Expression Statements- Compound Statements- Control Statements

a. Expression StatementsAn expression followed by a semi-colon. It caused the expression to be evaluated.

Example:i = 0;i++;

a = 5 + i;y = (m * x) + b;printf("Slope = %f", m);;

b. Compound StatementsA group of individual statements enclosed within a pair of curly braces { and }. It does not

end with a semicolon after }. It is also called Block Statements.

Example:{

float start, finish;

start = 0.0;finish = 400.0;

distance = finish start;

time = 55.2;speed = distance / time;

printf("Speed = %f m/s", speed);}


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c. Control StatementsUsed for loops, branches and logical tests. Often require other statements embedded within

them.

Before exploring more in to Control Statements, we must understand Boolean expressions.

Boolean expressions return integers:

- 0 if expression evaluates as FALSE- Non-zero if expression evaluates as TRUE (usually returns 1, but this is not

guaranteed)

Example:intmain(void){

int x = 5, y, z;

y = (x > 4);z = (x > 6);

while (1);

}

y = 1 (TRUE)

z = 0 (FALSE)


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i. if Statement

Standard Syntaxif (expression) statement

expression is evaluated for Boolean TRUE (0) or FALSE (=0), if TRUE, then

statement is executed.

Flow diagram of if statement

Example:{

int x = 5;

if (x){

printf("x = %d\n", x);}while (1);

}

if statement may has several combination of:

a. Nested if statementb. if-else statementc. if-else if statement

expression statement

START

END

expression statement

START

END

TRUE

FALSEexpression = 0

expression 0


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ii. switch StatementStandard Syntaxswitch (expression){

case const-expr1: statements1

.

.

.case const-exprn: statementsndefault: statementsn+1

}

expression is evaluated and tested for a match with the const-expr in each case

clause. The statements in the matching case are executed.


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Flow diagram of default switch statement

Flow diagram of modified switch Statement

Const-expr1=

expression?

START

END

statement2

statement1

Const-expr2=

expression?

statementn+1

Const-exprn=

expression?statement

n

Const-expr1=

expression?

START

END

statement2

statement1

Const-expr2=

expression?

statementn+1

Const-exprn=

expression?statement

n

Notice that each statementfalls through to the next

This is the default behavior

of the switch statement

Const-expr1=

expression?

START

END

Const-expr2=

expression?

statementn+1

Const-exprn=

expression?

statement1

break;

statement2

break;

statementn

break;

Const-expr1=expression?

START

END

Const-expr2=

expression?

statementn+1

Const-exprn=

expression?

statement1break;

statement2

break;

statementn

break;

Adding abreak

statement to eachstatement block willeliminate fallthrough, allowingonly one caseclause's statement

block to be executed


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Example:switch(channel){

case 2: printf("WBBM Chicago\n"); break;case 3: printf("DVD Player\n"); break;case 4: printf("WTMJ Milwaukee\n"); break;

case 5: printf("WMAQ Chicago\n"); break;case 6: printf("WITI Milwaukee\n"); break;case 7: printf("WLS Chicago\n"); break;case 9: printf("WGN Chicago\n"); break;

case 10: printf("WMVS Milwaukee\n"); break;case 11: printf("WTTW Chicago\n"); break;case 12: printf("WISN Milwaukee\n"); break;

default: printf("No Signal Available\n");}


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iii. for StatementAlso being called as for loop.

Standard Syntaxfor(expression1; expression2; expression3)

statement

- expression1initializes a loop count variable once at start of loop (e.g. I = 0).

- expression2is the test condition: the loop will continue while this is true (e.g. I


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iv. while StatementOften called while loop.

Standard Syntaxwhile (expression) statement

- Ifexpression is TRUE, statement will be executed and then expressionwill be re-evaluated to determine whether or not to execute statement again.

- It is possible that statement will never be executed ifexpression is FALSE

when it is first evaluated.

Flow diagram of while Statement

Example:

Expected result:

Loop iteration 0

Loop iteration 1Loop iteration 2

Loop iteration 3

Loop iteration 4

expression?

START

END

statementexpression?

START

END

statement

iinntt ii == 00;;

wwhhiillee ((ii


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v. do-while StatementAlways called do-while loop

Standard Syntaxdo statement while (expression);

- statement is executed and then expression is evaluated to determine whetheror not to execute statementagain.

- statement will always execute at least once, even if the expression is FALSE

when the loop starts.

Flow diagram of do-while Statement

Example:

Expected result:

Loop iteration 0

Loop iteration 1

Loop iteration 2

Loop iteration 3Loop iteration 4

Loop iteration 5

expression?

START

END

statement

expression?

START

END

statement

Loop counter incremented

manually inside loop

Loop counter initialized outside

of loop

Condition checked at end of

loop iterations

iinntt ii == 00;;

ddoo{{

pprriinnttff((""LLoooopp iitteerraattiioonn ##%%dd\\nn"",, ii++++));;

}} wwhhiillee ((ii


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vi. break StatementStandard Syntaxbreak;

- Causes immediate termination of a loop even if the exit condition hasnt been met.- Exits from a switch statement so that execution doesnt fall through the next case

clause.

Flow diagram of break Statement

Example:

Expected result:

Loop iteration 1

Loop iteration 2

Loop iteration 3

Loop iteration 4

expression?

START

END

break

statement

statement

expression?

START

END

break

statement

statement

TRUE

FALSE

iinntt ii == 00;;

wwhhiillee ((ii


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vii. continue StatementStandard Syntaxcontinue;

- Causes program to jump back to the beginning of a loop without completing thecurrent iteration.

Flow diagram of break Statement

Example:

Expected result:

Loop iteration 1

Loop iteration 3

Loop iteration 4

Loop iteration 5

expression?

START

END

continue

statement

statement

expression?

START

END

continue

statement

statement

TRUE

FALSE

iinntt ii == 00;;

wwhhiillee ((ii


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7. Functions

Functions are self contained program segments designed to perform a specific, well defined

task.

- All C programs have one or more functions.- Themain( ) function is the minimum function needed.

- Functions can accept parameters from the code that calls them.- Functions usually return a single value.- Functions help to organize a program into logical, manageable segments.

Program Structure in C programming

drink(){...

be_merry(); return;

be_merry(){...return;

}

eat(){...return;

main(){

...eat();...drink();...


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Standard Syntax of function definition

Example:

int maximum(int x, int y){int z;

z = (x >= y) ? x : y;

return z;}

Standard Syntax of function calling

a. No parameters and no return value:foo( );

b. No parameters, but with a return value:x = foo ( );

c. With parameters, but no return value:foo(a, b);

d. With parameters and a return value:x = foo(a, b);

Syntax

ttyyppee iiddeennttiiffiieerr((ttyyppee11aarrgg11,,,,ttyyppeennaarrggnn))

{{ddeeccllaarraattiioonnss

ssttaatteemmeennttss

rreettuurrnneexxpprreessssiioonn;;}}

DDaattaa ttyyppee ooffrreettuurrnneexxpprreessssiioonn

NNaammee

PPaarraammeetteerrLLiisstt((ooppttiioonnaall))

RReettuurrnn VVaalluuee ((ooppttiioonnaall))HHeeaaddeerr

BBooddyy


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Function Prototypes

- Like variables, a function must be declared before it may be used.- Declaration must occur beforemain( ) or other functions that use it.

- Declaration may take two forms:o The entire function definitiono Just a function prototype the function definition itself may then be placed

anywhere in the program

Example:

iinntt aa == 55,, bb == 1100,, cc;;

iinntt mmaaxxiimmuumm((iinntt xx,, iinntt yy));;

iinntt mmaaiinn((vvooiidd))

{{cc == mmaaxxiimmuumm((aa,, bb));;pprriinnttff((""TThhee mmaaxx iiss %%dd\\nn"",, cc))

}}

iinntt mmaaxxiimmuumm((iinntt xx,, iinntt yy)){{rreettuurrnn ((((xx >>== yy)) ?? xx :: yy));;

}}

Function is declared with

prototype before use in main ( )

Function is defined after it is used

in main ( )


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8. Creating Project using MPLAB + HI-TECH C PRO Compiler

To start MPLAB IDE and open project for PIC16F series, please follow the step below:

1. Double click on the icon installed on the desktop after installation or selectStart>Programs>Microchip> MPLAB IDE v8.20a>MPLAB IDE. A screen will

display the MPLAB IDE logo followed by the MPLAB IDE desktop as in diagrambelow.

2. The next step is to create a project using the Project Wizard. A project is the way thefiles are organized to be compiled and assembled. We Choose Project>Project

Wizard.


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3. From the Welcome dialog, click onNextto proceed.

4. The next dialog (Step One) allows you to select the device. In this example,PIC16F877A was selected from the drop down menu. ClickNext>.


32/39



5. The next step of the Project Wizard is sets up the language tools that are used withthis project. Select HI-TECH Universal Toolsuite in the Active Toolsuite list box.

Then select HI-TECH ANSI C Compiler in the Toolsuite Contents box. When you

are finished, clickNext.

6. Step three of the project wizard allows user to create new project file.


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7. For an example, a folder named Projectwas first created at Desktop.

8. Then open the folder, project. Project named project can be created by typing theproject name in the column for File name, and clickSave.


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9. Diagram below shown the Project project had been created and the directory. ClickNext>.

10.Step four of the project wizard allow user to add existing file to the project, however,for this example, no files will be added. Please clickNext> to proceed.


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11.A summary will be shown at the end of project wizard, all the project parameters areshown. Please clickFinish to exit from project wizard.

12.After pressing the Finish button, review the Project Window on the MPLAB IDEdesktop. It should look like the diagram below. If the Project Window is not open,

please select View>Project.


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13.In this example, sample source code for Cytron DIY project, PR23 will be added tothis project. The sample source code can be downloaded at

http://www.cytron.com.my/PR23.asp . Diagram below show the sample source code,

PR23.c being copied and pasted in the folder,project.

14.To add file in Source Files, right click on the Source Files, then click onAdd Files,diagram below shown the example for add file to Source Files


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15.After clicking onAdd Files, a window pop out, do make sure the Files of type isAllSource Files(*.asm;*.c), then browse to the folderProject to add in PR23.c. User

can select the file, PR23.c, and click open to add the file.

16.Diagram below shown PR23.c added to the project.


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17.After added the source file, user can open PR23.c file in this workspace and try tocompile it. Diagram below shown opened PR23.c file. To compile, user can go

Project>Build or the build icon (in red circle) on menu bar as shown in diagram

below.

18.After build success, a message Build successful! will appear in output window likeshown in diagram below.


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9. Starting a PIC Program

There are basic steps to start a program for PIC microcontroller

a. Create a project.

b. Create a C file.

c. Place some comments on top of C file.

d. Include necessary header file.

e. Write configuration bit.

f. Function prototype declaration, global variables.

g. Start main function, void main ().

h. 1st thing after PIC reset, it will come to main function and look at first program line.

Thus program write must initialize the PIC Input, Output, Analog input, UART, and

also other peripherals which going to be used in later program.i. Also please ensure the initial stage of output is not activated after reset.

Prepared by

Cytron Technologies Sdn. Bhd.19, Jalan Kebudayaan 1A,

Taman Universiti,

81300 Skudai,

Johor, Malaysia.

Tel: +607-521 3178

Fax: +607-521 1861

URL: www.cytron.com.my

Email: [email protected]

Date post:	04-Apr-2018
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