Introduction to Programming in C
Douglas C. Schmidt
University of California, Irvine
Based on Material Prepared by
Robert C. Carden IV, Ph.D.
Unisys Corporation
Mission Viejo, California
Required textbooks
David R. Brooks, C Programming: The Essentials For Engineers And Scientists,
Springer, New York.
Al Kelley and Ira Pohl, A Book On C, fourth edition, The Addison-Wesley Publishing
Company, Reading, Massachusetts
Gamma, Helm, John, and Vlissides, Design Patterns: Elements of Reusable Software
Components, The Addison-Wesley Publishing Company, Reading, Massachusetts
Recommended textbook
Brian Kernighan and Dennis Ritchie, The C Programming Language, second edition,
Prentice Hall, New Jersey.
Recommended books on the C language
Kamal B. Rojiani, Programming in C with Numerical Methods For Engineers,
Prentice Hall, New Jersey.
A-Series C Manual (Unisys Corporation), reference number 3950 8775-000, New
Jersey.
ANSI Draft on the C Programming Language, X3.159-1989
Copyright (c) 1998 by Robert C. Carden IV, Ph.D.
2/12/2016
Introduction to Programming in C
Recommended books covering advanced C language topics
Narain Gehani, An Advanced C Introduction: ANSI C Edition, Computer Science
Press, Rockville, Maryland
Andrew Koenig, C Traps and Pitfalls, Addison-Wesley Publishing Company,
Reading, Massachusetts
1-2
Introduction to Programming in C
Steven R. Lerman, Problem Solving and Computation for Scientists and Engineers:
An Introduction Using C, Prentice Hall, New Jersey
W. Richard Stevens, Advanced Programming in the UNIX Environment, AddisonWesley Publishing Company, Reading, Massachusetts
W. Richard Stevens, UNIX Network Programming, Addison-Wesley Publishing
Company, Reading, Massachusetts
Robert Sedgewick, Algorithms in C, Addison-Wesley Publishing Company, Reading,
Massachusetts
Additional references
Mark Allen Weiss, Data Structures and Algorithm Analysis, The
Benjamin/Cummings Publishing Company, Redwood City, CA
Paul Wang, An Introduction to Berkeley Unix, Wadsworth Publishing Company,
Belmont, CA
Peter A. Darnell, Philip E. Margolis, Software Engineering in C, Springer-Verlag,
New York, NY.
P.J. Plauger, The Standard C Library, Prentice Hall, Englewood Cliffs, NJ
1-3
Introduction to Programming in C
Class Objectives

The objectives of this class are as follows:




Teach you how to read C programs
Teach you how to write C programs
Teach you how to debug C programs
Teach you how to design good C programs

This is a class for developers, not managers
 Managers are certainly invited to attend, but they must plan to
do real work

If you are taking this class to see what C is all about without
planning on really learning it and programming it, you are in the
wrong class!
1-4
Introduction to Programming in C
How to Succeed in this Class

Attend class
 "90 percent of life is just showing up." --Woody Allen
 Exams are heavily based on material presented in class…

Never miss more than one consecutive week of classes
 If you just have to take that two week vacation, plan it so that
you only miss one week of classes -- really!
 Missing even one class will severely limit your ability to keep
up, particularly wrt the exams

Read ahead

Do the homework
 Students with a previous programming (e.g. Pascal or C++)
background should plan on spending 5-10 hours per week
 Students with a no programming background but computer
literate 10-20 hours per week
 Students with a no programming background and no computer
experience 20-30 hours per week...you will be spending a lot of
time struggling with the tools as well as learning how to
program
 The best plan of action is to do a little bit of the lab assignment
work each day, particularly if you have a home computer
 The worst plan of action is to do everything the night before
the homework is due

Ask questions
1-5
Introduction to Programming in C
How to Fail in this Class

Miss two consecutive weeks of class sessions

Try to survive without access to a C compiler
 You learn C by doing, i.e., you must write C programs,
compile them, and run them

Never spend any time on this outside of class

Do not attempt any of the homework

Habitually show up late for class or habitually leave early

The bottom line is that you will get out of this class
what you put into it!!!

To succeed, you need to spend at least 5 to 10 hours per week
on your own
1-6
Introduction to Programming in C
Overview of a Computer - Hardware
Reference: Brooks, Chapter 1; KP, Chapter 1
 Central Processing Unit (CPU) controls the flow of instructions and data and
performs the necessary manipulation of data
 Primary storage (memory) is used to store information for immediate access by the
CPU
 Note that there are many levels of cache used in primary storage
 Secondary storage devices (e.g., the hard drive, CD-ROM drives, tapes, etc.) provide
permanent storage of large amounts of data, but are much slower than primary
storage
 Input and Output devices provided interfaces between the computer and the user
Secondary
Storage
Primary
Storage
Input
Devices
Control Unit
Arithmetic
Logic Unit
Central Processing Unit
(CPU)
1-7
Output
Devices
Introduction to Programming in C
Overview of a Computer - Data Representation
 The first computers used vacuum tubes to hold data
 Vacuum tubes have two states - ON and OFF
 An ON state represents a 1
 An OFF state represents a 0
 Eight vacuum tubes strung together can represent an 8 digit string of 0s and 1s
 Put another way, this string is an 8 digit binary (base 2) number
 We use decimal (base 10) numbers in our daily life
 A decimal number is a string of digits whose values are drawn from the set
{0,1,2,3,4,5,6,7,8,9}
 In general, a number system is simply a way of representing numbers
 A number system has a base (the number of digits used in the number system)
 Consider a number in a base b number system:
an an 1  a1a0

The value of this number is:
a n b n  a n 1b n 1    a1b1  a 0 b 0
 A binary number has a base of 2 where the valid digits are 0 or 1
 E.g., 1001 binary == 9 decimal (1*8 + 0*4 + 0*2 + 1)
 An octal number has a base of 8 where the valid digits are 0 through 7
 E.g., 031 octal == 25 decimal (3*8 + 1)
 A decimal number has a base of 10 where the valid digits are 0 through 9
 E.g., 2000 decimal == 2000 (Y2K bug ;-))
 A hexadecimal number has a base of 16 where the valid digits are 0 through F, i.e.
{0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F}
 E.g., xABBA hex == 43962 decimal (10*4096 + 11*256 + 11*16 + 10)
1-8
Introduction to Programming in C
Overview of a Computer - Data Representation (2)
Powers of 2
2^0
2^1
2^2
2^3
2^4
2^5
2^6
2^7
2^8
2^9
2^10
1
2
4
8
16
32
64
128
256
512
1024
2^11
2^12
2^13
2^14
2^15
2^16
2^17
2^18
2^19
2^20
2^21
1K
2048
4096
8192
16,384
32,768
65,536
131,072
263,144
524,288
1,048,576
2,097,152
2K
4K
8K
16K
32K
64K
128K
256K
512K
1M
2M
1 KILO = 2^10 = 1024
1 MEG = 2^20 = 1024*1024
= 1,048,576
1 GIGA = 2^30 = 1024*1024*1024 = 1,073,741,824
 To evaluate a binary number, say 101101, simply add up the corresponding powers
of 2:
101101  1  2 5  0  2 4  1  2 3  1  2 2  0  21  1  2 0
 32  0  8  4  0  1  45
1-9
Introduction to Programming in C
Overview of a Computer - Hexadecimal Numbers
 A hexadecimal number is a string of hexadecimal digits
 Digits A, B, C, D, E, F represent the numbers 10, 11, 12, 13, 14, and 15
 Hexadecimal is popular in the computer field because it can be used to concisely
represent a long string of binary digits
 Consider a 16 digit binary number:
1011000111000101
 Break this up into groups of 4:
1011
0001
1100
0101
 Convert each group of 4 into decimal:
11
1
12
3
 Then convert each decimal number into hex:
B1C3
 And you now have the number: Baker 1 Charlie 3
Able
Baker
Charlie
Dog
Easy
Fox
=
=
=
=
=
=
A
B
C
D
E
F
=
=
=
=
=
=
10
11
12
13
14
15
=
=
=
=
=
=
1010
1011
1100
1101
1110
1111
 By the same token, the HEX number 3F2C1596 represents the binary string:
0011 1111 0010 1110 0001 0101 1001 0110
1-10
Introduction to Programming in C
Overview of a Computer - Primary Storage
 Primary storage, also known as main memory or RAM (random access memory) is
used to store information for immediate access by the Central Processing Unit
(CPU)
 Memory can be viewed as a series of memory cells with each cell having its own
individual address
 E.g., think of a bank of mailboxes at a post office
 The information contained in a memory cell is called the contents of that cell
 Memory cells can be used to store data, such as characters or numbers
 Internally, of course, they are all numbers, but we can choose to interpret some
numbers as characters
 They can also be used to store program instructions
 These are “special” numbers that are meaningful to a CPU!
 The smallest unit of computer storage is a bit, as in binary digit
 Most computers group bits together to form larger entities
 E.g., 8 consecutive bits often form a byte and 32 consecutive bits often form a
word
 A word on an Intel 286 computer is 16 bits or 2 bytes
 A word on an Intel 386, 486, and Pentium computers is 32 bits or 4 bytes
 The next generation of Intel computers (e.g. the Merced) will use 64 bit words,
i.e. 8 bytes
 The DEC Alpha computer is currently using 64 bit words
 Many mainframe computers, such as the Unisys A-Series, use 48 bit words
 Memory cells in a computer are typically one byte or one word in size
 A word is a unit of information that can be transferred to and from memory




A kilobyte of memory, as in 1K, is 1024 bytes of memory
A megabyte of memory, as in 1M, is 1024K of memory, or 2^20 bytes
A gigabyte of memory, as in 1G, is 1024M of memory, or 2^30 bytes
Note that a 32 bit word can represent 2^32 different possible values
1-11
Introduction to Programming in C
Programming Languages - Low Level Languages
 Computers only do what they are told to do
 Except in Hollywood movies, e.g., 2001, Terminator 2, the Matrix, etc. ;-)
 In order for a computer to perform a task, it must be given a series of specific
instructions in a language it can understand
 The fundamental language of any computer is its machine language
 This is typically sequences of zeroes and ones
 In the very early days of computers, this was the only way one could write
programs!!!
 To relieve the suffering of these early programmers, a higher level language called
assembly language was developed
 Assembly language contains mnemonic words and symbols for the binary
machine instructions
 An assembler maps assembly language instructions into machine language
instructions
 Assembly language programming is indeed a significant improvement over machine
language programming
 However, it has the following drawbacks:
 Machine dependent - each computer architecture has its own unique assembly
language
 Low level instructions - writing programs is very time consuming, tedious,
and error-prone
1-12
Introduction to Programming in C
Programming Languages - High Level Languages
 A general trend in computing over the past 4 decades is to elevate programming
from low level to higher level languages
 I.e., high level languages are geared more toward people writing the programs
rather than the computer
 Assembly language instructions map directly to machine instructions
 High level language instructions must be translated/compiled into machine
instructions
 High level languages are more “problem-oriented” than assembly/machine
languages
 E.g, they require little or no knowledge of the underlying computer architecture
 Learning how to write/debug programs in high level languages is much easier and
less error-prone than learning how to write/debug equivalent programs in assembler
 E.g., high level languages required fewer statements to do the same thing as
assembler
 Programs written in high level languages can be ported much more easily to
different computer architectures
 E.g., the compiler encapsulates the machine-dependent details of the target
assembly language
 A special program called a compiler is needed to translate a program written in a
high level language into assembly code (which is then transformed into native
machine code by an assembler)
 The statement written in the high level language are called source code
 The compiler/assembler's output is called object code
Source Code
Compiler
Assembler
1-13
Object Code
Introduction to Programming in C
Language Taxonomy
FORTRAN
COBOL
ALGOL
ASSEMBLER
PL/1
FORTRAN IV
B,BCPL
BURROUGHS
EXTENDED
ALGOL
FORTRAN77
SMALLTALK
APL
ALGOL68
COBOL85
PROLOG
LISP
C
PASCAL
ANSI C
C++
MODULA-2
E
ADA
1-14
Introduction to Programming in C
History of C
C
1970'S
Early 1980's
Late 1980's
TRADITIONAL C
ANSI C
[OR STANDARD C]
Add void type
enumeration
struct as parameter
other improvements
Add void *
function prototypes
new function definition syntax
minimum standard library
more functionality to preprocessor
Add const and volatile
American
National
Standards
Institute
X3J11 Committee
1-15
Introduction to Programming in C
Significant Points About C








Small number of keywords
Widely available, particularly on personal computers and workstations
Can be used very portably
 Standard library
 Preprocessor may be used to isolate machine dependent code
 Unlike Pascal, which has many dialects
Native language of UNIX (tm) and Windows NT
Terse
 Powerful set of operators
 Statements can be very powerful
 Some are bit level operators
 Designed to be implemented efficiently on many machines
Modular -- functions
 Parameters are typically passed `by value’
 No nested functions
Syntax is complicated
Semantics of certain features are complex and error-prone
1-16
Introduction to Programming in C
A Comparison of Programming Language Philosophy
Pascal



Strict Parent (a “bondage and discipline” language ;-))
Restricts programmer for his/her own good
A white, automatic transmission automobile with lots of safety features (e.g., air
bags, controls that limit speed to 55 miles per hour and prohibit leaving the lights on
or locking the keys in the car)
C



A permissive, easy going parent (a ‘lassize-faire’ language ;-))
Assumes that the programmer knows what he/she is doing and will assume
responsibility for his/her actions. (Some describe it as a “gun with which you can
shoot yourself in the foot.”)
A bright red ’65 Corvette with a big block engine, manual transmission, optional
seat belt, and with fuzzy dice hanging from the rear view mirror.
C++



A less permissive, yet open minded parent (e.g., ‘Thomas Huxtable’ ;-))
Assumes that the programmer generally knows what he/she is doing, but provides
more checking by default. (“With C++ it’s harder to shoot yourself in the foot, but
when you do, you’ll blow off both of your legs” – Bjarne Stroustrup)
A bright red 2000 Corvette with a 6 speed manual transmission, air bag, and heads
up display, many on board computers
1-17
Introduction to Programming in C
Example C Program
/*
File: hello.c
Description: Prints a greeting to stdout.
Author: Douglas C. Schmidt <schmidt@uci.edu>
*/
#include <stdio.h>
int main (void) /* execution starts in main */
{
printf ("Hello world.\n");
return 0;
}






All C programs must have a function in it called main
Execution starts in function main
C is case sensitive!
Comments start with /* and end with */. Comments may span over many lines.
C is a “free format” language.
The #include <stdio.h> statement instructs the C compiler to insert the entire
contents of file stdio.h in its place and compile the resulting file.
1-18
Introduction to Programming in C
Compiling a C Program

On a personal computer using Visual Studio, you will create a .c file, e.g. hello.c (as
in the previous example). You will then compile it to produce a .exe file (e.g.,
hello.exe) and perhaps a .obj file (hello.obj). Consult your compiler documentation
(each one is different).
1-19
Introduction to Programming in C
 In Visual Studio, do a File|New and you will see the following dialog...
1-20
Introduction to Programming in C
 Here, you must first select Win32 Console Application. Then press the ... button
that appears to the right of the Location
1-21
Introduction to Programming in C
 Now choose the location. You may need to create a folder on your file system. In
this case, I brought up the Windows NT explorer and created the new folder Ece11s98. Whatever you do, you should place the project in a place such that you can
easily find it later.
1-22
Introduction to Programming in C
 Now that you have specified a Location, i.e. a folder where you want your project
created, you should see the following...
1-23
Introduction to Programming in C
 Now, specify the name of your project. Visual Studio will create a folder
underneath the one you specified for Location by that name. This will also become
the name of your executable... Finally, click on the OK button to record your
selection.
 It is very important that you do each of these initial steps in the exact order that I
have described above. That is, first specify that you want a Console Application,
then specify the location, then specify the project name. Do not forget any of these
steps. In other words, pay attention!!!
1-24
Introduction to Programming in C
 As a result, you will see the following in Visual Studio
 Notice that the Workspace window now has three tabs. It has a ClassView tab, a
FileView tab, and an InfoView tab. Select (point the mouse to) the FileView tab.
1-25
Introduction to Programming in C
 After selecting the FileView tab, you should see the following. Notice what appears
in the Workspace window...
1-26
Introduction to Programming in C
 Now we need to create a source file and include it in the project. If we do the
correct sequence of steps, Visual Studio will automatically include the new file into
the project.
 Do a File|New and select Text File and then specify a File name. Do not accept the
default choice, Active Server Page (or whatever happens to be the default). Do not
select C/C++ Header File. Do not select C++ Source File. Select Text File. Do not
forget to type in the file name, i.e. hello.c (or whatever you wish to call it), but it
must end with .c !!! The file suffix tells Visual Studio what type of file this is so it
knows which compiler to invoke on it. Finally, click OK to select your choice.
1-27
Introduction to Programming in C
 As a result of your efforts, you should see the following.
1-28
Introduction to Programming in C
 I usually move the windows around at this point, adjusting the sizes.
 Type in the program.
1-29
Introduction to Programming in C
 If you click on the + by Hello files under Workspace, you will see a list of all of the
files in your project
 Build your program by selecting the Build|Build menu option
1-30
Introduction to Programming in C
 Run it (Build | Execute)
Now let's look at the files:
Hello.dsw: this is your WORKSPACE
Hello.dsp: this is the project build file
These two files, along with hello.c are worth saving.
1-31
Introduction to Programming in C
 The program we just built is HELLO.EXE under the Debug directory
 Because it is a CONSOLE application, we can run it directly from our Windows NT
command (or Windows 95 Dos) prompt.
 When I typed hello below at the Dos prompt, Windows ran the program hello.exe.
Below you can see the results of this run.
1-32
Introduction to Programming in C
Compiling Under UNIX
To compile a C program under UNIX, one may do it in the following ways:
% cc hello.c
This compiles the file and creates an executable named a.out
% cc hello.c -o hello
This compiles the file but renames the executable hello
% cc -c hello.c
This compiles the file but does not link it, thus producing an object module which may
be linked later on. That file, by default, is hello.o
% cc hello.o -o hello
This links the object file hello.o to create the executable hello
Under UNIX, suffixes are important (i.e., .c versus .o). They tell the compiler what
type of file they are, i.e. a C program file versus an object module.
% cc foo.o bar.o -o fubar
This links two separately compiled modules into an executable named fubar.
1-33
Introduction to Programming in C
The compiling process -- overview
C Program -- foo.c
% cc -c foo.c
cpp -- C preprocessor
Handles #-directives; removes comments
foo.E
ccom -- C Compiler
compile program
C Optimizer
(optional)
foo.s
as -- assembler
foo.o
1-34
Introduction to Programming in C
Compiling process -- translation phases (ANSI)
1. Physical source file characters are mapped to the source character set (including
new-line characters and end-of-file indicators) if necessary. Trigraph sequences are
replaced by corresponding single-character internal representations.
2. Each instance of a new-line character and an immediately preceding backslash
character (\) is deleted, splicing physical source lines to form logical source lines.
3. The source file is decomposed into preprocessing tokens and sequences of whitespace characters (including comments). A source file shall not end in a partial
preprocessing token or comment. Each comment is replaced by one space character.
New-line characters are retained.
4. Preprocessing directives are executed and macro invocations are expanded. A
#include preprocessing directive causes the named header or source file to be
processed from phase 1 through phase 4 recursively.
5. Each source character set member and escape sequence in character constants and
string literals is converted to a member of the execution character set.
6. Adjacent character string literal tokens are concatenated and adjacent wide string
literal tokens are concatenated.
7. White-space characters separating tokens are no longer significant. Each
preprocessing token is converted into a token. The resulting tokens are syntactically
and semantically analyzed and translated.
8. All external object and function references are resolved. Library components are
linked to satisfy external references to functions and objects not defined in the
current translation. All such translation output is collected into a program image
which contains information needed for execution in its execution environment.
1-35