Unit 2 Getting Started with C Using an Integrated Development Environment Introduction to C...

Unit 2

Getting Started with CUsing an Integrated Development

Environment

Introduction toC Programming

Review of Unit 1

Unit 1: Review

A Computer System is … Hardware:

Central processing unit (CPU)Main memory (RAM, ROM)Secondary memory (Hard disk, CD, DVD, flash

drive, etc)Input devicesOutput devicesNetwork interfacePower supply

Software:FirmwareOperating systemApplication programs

What is a Software “Program”? A set of instructions Performs a specific task Required to make the hardware “do

something” The hardware “runs” or “executes” it Must be in main memory (RAM or ROM) Is written in machine language (specific to

a CPU) Consists of binary ‘1’s and ‘0’s

What Programs Have in Common Programs process information:

Information is stored in the form of binary dataDifferent types of information use different data

typesPrograms acquire input dataPrograms produce output data

Programs are implementations of algorithms:Algorithms are precise solutions to problems

Programs are written in programming languages:May be compiled (translated) to machine languageMay be compiled to intermediate form and then

interpreted

Embedded Systems Found everywhere as part of electronic devices Examples: Watches, calculators, appliances,

irrigation and lighting systems, copiers, traffic lights, MP3 players

Pre-programmed computer Dedicated to a few functions inside a device Often must be real-time (respond “immediately”

to events) Non-stop computing (continuously functioning) Traditionally viewed as non-reprogrammable Reprogrammability is becoming commonplaceTherefore, programming is essential to

electronics students!

Creating a Program Use problem solving skills Create an algorithm Implement the algorithm in a programming

language Understand the programming model Use specialized tools Use software engineering methodology

Use Problem-Solving Process

Heuristics (strategies) for successful problem solving

Five-step process (from Strategies for Creative Problem Solving, Fogler et al.):1. Define the problem2. Generate possible solutions3. Evaluate and decide on a solution4. Implement the solution5. Evaluate the solution

Develop Problem-Solving Skills

A good programmer is an effective problem solver Has a belief that problems can be solved through

analysis Develops a high level of problem-solving skills:

Active – Makes sketches, draws figures, asks questions

Methodical – Keeps track of progress in solving the problem

Detail-orientedTakes great care to understand facts and

relationshipsChecks and re-checks for accuracy

Create an Algorithm

Develop an algorithm before writing a program

Use precise statementsBased in mathematics and logicClear and concrete language

Define a step-by-step process Goal is solution to a problem

Software Development Method1. Specify the problem requirements2. Analyze the problem3. Design the algorithm to solve the problem4. Implement the algorithm as a program5. Test and verify the completed program6. Maintain and update the program

Analyzing the Problem

Requires identifying the …Inputs – the data available to work withOutputs – the desired results

Including the format of the outputAdditional requirementsConstraints

Producing the Algorithm List of steps from beginning to end Begin at step 1, have a specific step to end Don’t try to get every detail at first Use top-down design:

Break the problem into subproblemsSolve each subproblem individuallySimilar to outlining a written paper

Use pseudo-code combined with flowcharting

Desk-check the algorithm

Begin and End Shapes These shapes are used to begin and end a

flowchart The beginning shape has the algorithm

name as its label The end shape contains the word “End”

Rectangle Shape – Actions Rectangle has one entry and one exit The text in the rectangle is pseudo-code

corresponding to one step in the algorithm

Diamond Shape – Decision Point One entry, two exits (one for “yes”, the

other for “no”) Contains one question, with yes/no answer

Selection Shape Selection is an extension of the decision

point Instead of a question, the diamond contains

a value The value selects which branch to take One “other” branch is used for all other

values that don’t have a branch

Connector Shape – On-page Use for a connection on same page Shape shows connection from one point to

another

Left shape can be used multiple times Right shape, used once, shows the destination

of connection

Connector Shape – Off-page Use for a flowchart larger than one page Shape shows connection from one page to another

Left shape can be used multiple times Right shape, used once, shows the destination of

connection Visio automatically creates a new page when this

shape used

Introducing the C Language

Unit 2: Introduction to the C Programming Language

Origin and History of C

Lineage:BCPL (Martin Richards, Univ of Cambridge, 1966)

B programming language (Ken Thompson et al., Bell Labs, 1969)

Creation:Dennis Ritchie of AT&T Bell Labs1969-1973Supported development of UNIX

Peculiarities:Terse language – author of C didn’t like typingWidespread use led to many variations in 1980sSyntax and idioms can be frustrating to learn

Standardization By mid-to-late 1980s:

Many differing implementations on different computersIncompatible extensionsIncompatibilities in "standard" libraries

American National Standards Institute (ANSI) – 1989:Created a standard, now called C89

International Organization for Standardization (ISO) – 1990:Adopted ANSI standard, now called C90 (same as C89)C99 - Revision published in 1999 (slow adoption, Pelles C is

C99)C1X - New revision underway

Ensures that all standard C implementations are compatible:Defines the meaning and extent of compatibility

C Has Many SuccessorsSubsequent creation of many “C-like” derivative languages:Embedded C (ISO C Standards Committee, 2008)C++ (Object-oriented, Bjarne Stroustrup, Bell Labs)C# for .NET (Object-oriented, Anders Hjelsberg, Microsoft)Java and derivatives (Sun Microsystems)Perl (structurally similar to C)Ruby… and many other less popular languages

C is a Procedural Language C is a high-level procedural language:

In C, a procedure is called a functionProgram divided into a number of functionsEach function consists of steps called statementsStatements may use other functions

Matches top-down design:Sub-problem solved with a functionFunction implements an algorithm

Functions operate on data in the form of:Constants - values that do not change, such as

12, 2.5, and “bacon”Variables - named locations in memory

The “Hello, World!” ProgramFlowchart for the traditional first C program:

Let’s see what it takes to implement this in C.

The “Hello, World!” Program in C

#include <stdio.h>

/* Our first C program */

int main(void){

printf("Hello world!\n");return (0);

}

Structure of a C Program


Each Program has a main() This program has a function named main() The compiler looks for main() as the starting

point The loader starts the program at main() The function body is inside the { and }

(braces)

#include <stdio.h>


int main(void){


}

Statements Function body has one or more statements (this

one has 2) Each statement is a step, like a rectangle on a

flowchart All statements must end with a semicolon (shown

in red)(You may, at first, feel frustrated by the semicolons)

#include <stdio.h>


int main(void){


}

Use of a Library Function This main() uses another function named printf() The printf() function is in the Standard I/O (stdio)

library The standard libraries are supplied with the C

compiler The #include line allows us to use the stdio.h library

header

#include <stdio.h>


int main(void){


}

A Function's return Statement

The caller of a function is that program which started it running

Functions can return a value back to the caller The main() function always returns zero (0) to the OS The word int indicates the type of value that main()

will return

#include <stdio.h>


int main(void){


}

Constant Values A C program can contain various constant values The text inside the double-quote characters is called

a string constant The zero character, 0, is called an integer constant

#include <stdio.h>


int main(void){


}

Miscellaneous A comment starts with /* and ends with */ The entire comment is ignored by the compiler Comments are included in programs to aid in

human understanding The word void in main() will be explained in a

later class

#include <stdio.h>


int main(void){


}

Algorithm to Convert miles to km1. Output “Convert miles to kilometers”2. Output “Please enter the distance in miles”3. Input dist_in_miles4. Convert dist_in_miles to kilometers

a)Multiply dist_in_miles by 1.609b)Put the result in dist_in_kms

5. Output “The distance in kilometers is”6. Output dist_in_kms7. End

This algorithm was presented in Unit 1

Program to Convert miles to km

#include <stdio.h>

int main(void){

double dist_in_miles, dist_in_kms;

printf("Convert miles to kilometers\n");printf("Please enter the distance in miles: ");scanf("%lf", &dist_in_miles);

dist_in_kms = 1.609 * dist_in_miles;printf("The distance in kilometers is: ");printf("%f", dist_in_kms);

return (0);}

The Statements Match the Algorithm

Each step in the algorithm becomes a statement:

#include <stdio.h>

int main(void){

double dist_in_miles, dist_in_kms;



return (0);}

Variables Must be DeclaredVariables used in the function must be declared before use:

#include <stdio.h>

int main(void){

double dist_in_miles, dist_in_kms; /* Declaration */



return (0);}

C Syntax Requires Exact Punctuation

Parentheses, brackets, and braces always are in matched pairs

Commas are used to separate items in a list A semicolon must end each statement

#include <stdio.h>

int main(void){

double dist_in_miles, dist_in_kms;printf("Convert miles to kilometers\n");printf("Please enter the distance in miles: ");scanf("%lf", &dist_in_miles);dist_in_kms = 1.609 * dist_in_miles;printf("The distance in kilometers is: ");printf("%f", dist_in_kms);return (0);

}

Some Special Words are Reserved

Reserved words have special use and meaning Functions cannot use reserved words as their names Variables cannot use reserved words as their names

#include <stdio.h>

int main(void){

double dist_in_miles, dist_in_kms;printf("Convert miles to kilometers\n");printf("Please enter the distance in miles: ");scanf("%lf", &dist_in_miles);dist_in_kms = 1.609 * dist_in_miles;printf("The distance in kilometers is: ");printf("%f", dist_in_kms);return (0);

}

C Reserved WordsThe C language has 32 reserved words:

auto double int structbreak else long switchcase enum registertypedefchar extern return unionconst float short unsignedcontinue for signed voiddefault goto sizeofvolatiledo if static while

This list is also in Appendix E of the textbook

The printf() Function The printf() function is in <stdio.h> library It creates formatted output for the console

display Can output a string of characters

printf("Hello World!\n");

Can output numeric data from constants or variables

printf("%f", 12.5);printf("%f", dist_in_kms);

The % character and the character(s) that follow are called conversion specifiers (Hanly book, et al, use term format placeholders).

The scanf() Function The scanf() function is in <stdio.h> library It performs formatted input from the console

keyboard Can input numeric data into variables

scanf("%lf", &dist_in_miles);

The '&' character is required to designate an input variable

The '%' character and the letter(s) that follow are conversion specifiers (or format placeholders).

We will come back to printf() and scanf() later

Variables and Data Types


Data Resides in Variables Variables must be declared to the compilerdouble dist_in_miles, dist_in_kms;

The compiler manages size and location in main memory

Programmer refers only to the variable's nameName should be descriptive of data in

variable Each variable also has a data type

The word that begins the declaration is the data type, for example, "double" as shown above

Variables Placed in Main Memoryby Compiler

Variable Name Rules ANSI C Rules:

Only letters, digits, and underscores (_ shift-minus)

Cannot begin with a digitUppercase is different than lowercaseCannot be a reserved word

Tips:Don't use a name found in a C standard libraryUse a standard coding style (we'll talk more

about this next unit)

Data Types in C int - An integer, positive or negative (signed)

whole number0 143 -213415

float - A signed number with fraction in scientific notation

24.7063 -0.148 3.0E8 -12.7E-6 double - Like float with twice the precision

24.7063000000 -0.148000000000(Once used sparingly as inefficient, now is the norm)

char - A single ASCII character'.' 'r' 'E' '4' ' ' '?'

Typical Usage of Numeric Data Types double

MoneyMeasurements of physical quantities

(distance, voltage, current)Very large and very small numbers

intCountersIndex (position in a list)Settings, positions of dials and controlsDigital and binary values

Advanced Data Types An int is typically 32 bits signed two's

complement binaryIts range is -2147483648 to 2147483647

signed or unsignedCan combine with int

signed int - same as an intunsigned int - positive numbers only 0 to 4294967295

short or longCan combine with int and unsigned int

short int - 16-bit binary -32768 to 32767unsigned short int - 16-bit binary 0 to 65535long int - on some machines can be a 64-bit integer

String Constants


String Constants Defined A string constant is zero or more characters

(A string constant can be empty) Each character takes one byte in memory

(An extra zero byte is used in memory at the end of a string)

Each character is encoded using the ASCII code

A string constant must begin and end with a double-quote(The quote characters are not stored in

memory)

String Constants - Examples "Hello World" "Hello" and "Hello " are different "134.5" is not a number, it's a string "!@#$%;" is a string containing punctuation

characters "" is the empty string " " is a string consisting of a space; it's not

empty "AF" and "af" are different - case

sensitive

String Escape Sequences Put special characters in a string or character constant Sequence of characters, starting with backslash \ Put quote or double-quote in a string or character

constant"\"Hi!\", we said." Single string of 15 characters

Put a backslash in a string or character constant"\\" A string with one backslash character

Put special codes in a string or character constant"\n" Makes console output start a new line"\t" Outputs a tab character'\g' Make a "beep" noise from the speaker

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