Structured Programming in C

1
Welcome to CPSC 206

• Structured Programming in C

2
Lecture Information

• http//people.cs.tamu.edu/ychen/Teaching/CPSC206

3
Midterm 1

• Time Sept 30, Thur., 800-915AM
• Location HRBB 124
• Closed book
• No textbook, No notes, No calculator
• You are required to bring
• Answer sheet SCANTRON (NCS MP90051 or
  0-101607-TAMU) (You can find it in MSC
  Bookstore)
• No. 2 pencils, eraser
• Student ID

4
Review 1

• Topic 1 Introduction to Computer Science
• Topic 2 Overview of C Language
• Chapter 1
• Section 1.1 1.8
• Chapter 2
• Section 2.1 2.12

5
Topic 1 Introduction to Computer Science

• Part I an overview of computer science.
• Part II computer hardware and software.
• Part III computer languages.

6
Introduction to Computer SciencePart I an
overview of computer science.

• What is computer Science?
• Basic idea about research areas in computer
  science.
• Architecture
• Operating System
• Computability theory
• Algorithm design
• Programming Language
• Compiler
• Complexity theory

7
Introduction to Computer SciencePart I an
overview of computer science.

• Basic idea about research areas in computer
  science. (contd.)
• Human-computer interaction
• Artificial Intelligence
• Software engineering
• Networking, Parallel and Distributed System.

8
Introduction to Computer SciencePart I an
overview of computer science.
Sample Question Software engineering focuses on
how to develop applications for networks. True of
False
False
9
Introduction to Computer SciencePart II
computer hardware and software

• Computer organization.
• Data representation
• Main Memory
• Central Processing Unit (CPU)
• Secondary Storage
• Input / Output
• Solving problems on computers.
• System Design
• Algorithm Development and Representation
• Programming

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Computer Organization

• Data Representation
• How data is stored and processed?
• All data is stored and processed in binary form,
  that is, as a series of 0s and 1s.
• The definition of Bit, Byte, Word

Sample Question The number of bits in one Bytes
is a) 4 b) 8 c) 16 d) 32 e) none of the above
b
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Computer Organization

• Data Representation
• Binary number
• Convert a decimal number to a binary number
• What is the decimal value of a binary number

Sample Question The decimal value of a binary
number 100001 is a) 33 b) 1 c) 100001 d) 17 e)
none of the above
a
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Computer Organization

• Data Representation (contd.)
• How a signed number is represented in binary
  form?
• In a binary representation, the leftmost bit is a
  sign bit followed by the magnitude bits.  
• Sign-bit 0 implies a positive number, 1 implies
  a negative number.
• How character is represented? (ASCII coding
  system)
• Each character is represented in a 7-bit format.

13
Computer Organization
Sample Question Consider the data representation
of signed integers using 4 bits, in which one bit
is used as the sign bit. The maximum decimal
integer that can be represented is ___ a) 1111 b)
111 c) 7 d) 15 e) none of the above
c
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Computer Organization

• Memory
• What is memory?
• It is part of a computers electronic circuitry
  holding the binary data which is processed by the
  computers program.

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Computer Organization

• CPU
• What does CPU stand for?
• Central Processing Unit (CPU)
• What is
• Control Unit, ALU, Program Counter, Instruction
  Counter?
• What is program? How a program is executed?
• Machine Cycle
• Hardware characteristics
• Clock speed
• MIPS

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Computer Organization

• Central Processing Unit (CPU)

CPU reads program instructions from main memory.
CPU executes one instruction at a time until
completion.
CPU
Arithmetic/Logic Unit (ALU)
Control unit
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Computer Organization

• Central Processing Unit (CPU) (contd.)

Program Counter (PC)
Instruction Counter (IC)
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Computer Organization

• Central Processing Unit (CPU) (contd.)
• What is program?
• Program is a set of instructions
• How a program is executed?
• Program is loaded into memory.
• In each Machine Cycle
• Fetch, Decode, Execute
• Machine Cycle is repeated until completion.

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Computer Organization

• Central Processing Unit (CPU) (contd.)
• In each Machine Cycle
• Fetch
• The control unit loads the instruction pointed to
  by PC to IC.
• PC is updated to the address of the next
  instruction.
• Decode control unit decodes the fetched
  instruction and determines the required action to
  take.
• Execute control unit activates the appropriate
  circuitry.

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Computer Organization

• Central Processing Unit (CPU) (contd.)
• Hardware characteristics
• The speed of a computer can be quoted as
• Clock speed, e.g. 100MHz means 100 million cycles
  per second.
• MIPS, a million instructions per second.

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Computer Organization

• Secondary Storage
• Mass storage devices
• Sequential storage tape.
• Random storage floppy disk, zip disk, CD-ROM,
  etc.
• Static storage.
• it doesn't require power to retain stored data.
• Slower speed.

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Computer Organization

• Input
• Keyboard, mouse etc
• Output
• Monitor, printer etc

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Computer Organization

• How CPU, Memory, Storage, Input and Output work
  together?
• IPOS Cycle

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Computer Organization

• I - Input

P - Process
O - Output
S - Storage
Binary Representation
P
CPU
Memory
Secondary Storage
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Introduction to Computer SciencePart II
computer hardware and software

• Computer organization.
• Data representation
• Main Memory
• Central Processing Unit (CPU)
• Secondary Storage
• Input / Output
• Solving problems on computers.
• System Design
• Algorithm Development and Representation
• Programming

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Solving problems on computers.

• System Design
• Top-down
• break the problem into smaller and smaller
  sub-problems until they can be solved trivially.
• Bottom-up
• start by designing the low-level details, and
  then decide how these will be put together to
  create the entire system

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Solving problems on computers.

• Algorithm Development and Representation
• What is algorithm?
• a specification of the series of steps which must
  be followed in order to solve a problem or
  accomplish a task.
• Algorithm Representation
• Pseudo Code
• Decision Trees
• Flow Charts

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Solving problems on computers.

• Programming
• What is programming?
• Programming is the process of translating a
  problems solution into instructions that a
  computer can process.

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Solving problems on computers.

• Programming Paradigms
• Procedural Programming is based upon the concept
  of the modularity.
• A main procedural program is composed of one or
  more modules. Each module is composed of one or
  more subprograms.
• Declarative programming
• describes to the computer a set of conditions and
  
• lets the computer figure out how to satisfy them.
  

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Solving problems on computers.

• Programming Paradigms
• Object oriented programming
• A computer program is composed of a collection of
  individual units, called objects.
• Operations are provided for each class of
  objects.
• Operations change the state of an object.
• To make the overall computation happen, the
  objects interact through their own operations and
  their own data.

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Introduction to Computer SciencePart III
Computer Language

• Why Computer needs language?
• Computer requires an unambiguous language
• Computer Language are designed to be unambiguous.
• Precedence and associativity determine precisely
  how expressions are evaluated.

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Introduction to Computer SciencePart III
Computer Language

• C language
• C is a general purpose programming language.
• C is a middle level language.
• It combines the elements of high-level language
  with the functionality of low-level language.
• C is a structured language.
• It allows programmer to divide program into
  modules.

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Introduction to Computer SciencePart III
Computer Language
There is only one programming language that a
computer can actually understand and execute its
own native binary machine code.

• Languages are classified as
• low level if they are close to machine code and
• high level if each language statement corresponds
  to many machine code instructions.

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• End of Review of Topic 1
• Introduction of Computer Science

35
Chapter 1

• Review Outline
• A brief history of C
• Features of C
• Get Ready to Program
• General form of a simple program
• main function
• variable declarations

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Chapter 1

• Review Outline (contd)
• initialization
• preprocessing directive
• include
• define
• printf and scanf
• printf
• \n
• scanf
• while statement

37
Chapter 1

• A brief history of C
• 1960s, CPL (Combined Programming Language)
• capable of both high level machine independent
  programming and would still allow the programmer
  to control the behavior of individual bits of
  data.
• too large for use in many applications.
• 1967, BCPL (Basic CPL) a scaled down version of
  CPL.
• In 1970, B a scaled down version of BCPL
• written specifically for use in systems
  programming.
• In 1972, C
• Dennis Ritchie returned some of features of BCPL
  to the B language in the process of developing C.

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Chapter 1

• 2. Features of C
• Small
• The core language of C is small
• Non-essential functionality, such as math
  functions or file handling, is provided by a
  standardized set of library routines.
• Portable
• easily moved from machine to machine.
• Powerful
• it is able to access low level commands
• Useful in writing system software
• Procedural Programming paradigm
• Allows programmer to divide program into modules.

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Chapter 1

• 3. Get Ready to Program
• The Programming Process
• Specify the task
• Discover an algorithm for its solution
• Code the algorithm in C
• Test the code
• The cycle of the programming process

edit
pico / vi
gcc / cc
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Chapter 1

• 4. General Form of a simple program

The general form of a program preprocessing
directives int main () declarations
statements
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Chapter 1

• 4. General Form of a simple program (Contd).
• main function
• Every program has a main function.
• The execution starts at main function.
• Declaration
• All variables in a program must be declared
  before they can be used.
• The data type of a variable specifies what kind
  of data can be stored in the variable.

42
Chapter 1

• 4. General Form of a simple program (Contd).

Sample Question int main() int c14,
c22 printf(Sum d\n, sumc) What is the
output? a) 6 b) 4 c) sumc d) error
d
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Chapter 1

• 5. Initialization
• A variable can be initialized when it is
  declared.
• Constants or constant expressions can be used to
  initialize a variable.
• Declared variables can be used to initialize a
  variable.
• a variable cannot be used before it has been
  declared.

44
Chapter 1

• 6. preprocessing directive
• include filename
• The preprocessor replaces the line with a copy of
  the named file.
• define A B
• It affects only those lines in the file that come
  after it.
• All occurrences (after this line) of the
  identifier A, except in quoted string, will be
  changed to B.

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Chapter 1

• 6. preprocessing directive (Contd)

Sample Question include ltstdio.hgt define Sumc
c1c2c3 int main() int c14,
c22 printf(Ave d\n, Sumc) What is the
ouput? a) 6 b) 4 c) sumc d) error
d
46
Chapter 1

• 6. preprocessing directive (Contd)

Sample Question include ltstdio.hgt define Sumc
c1c2 int main() int c14, c22 printf(Ave
d\n, Sumc) What is the ouput? a) 6 b) 4 c)
sumc d) error
a
47
Chapter 1

• 6. preprocessing directive (Contd)

Sample Question include ltstdio.hgt define Sumc
c1c2 int main() int c14, c22 printf(Ave
d\n, Sumc/2) a) 5 b) 3 c) 4 d) 2
a
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Chapter 1

• 7. printf and scanf
• Arguments control_string and other_arguments
• control_string contains formats, called
  conversion specifications, which are matched with
  other arguments.

49
Chapter 1

• 7. printf and scanf (contd)
• printf How to specify format using conversion
  specification?
• field_widthconversion_character
• field_width.precisionconversion_character
• Example
• printf(7.2f, 1.221)
• printf(7d, 1221)

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Chapter 1

• 7. printf and scanf (contd)
• printf How to specify format using conversion
  specification?
• field_widthconversion_character
• field_width.precisionconversion_character
• conversion_character how the data is printed?
• c character
• d decimal integer
• f floating-point number
• s, e, g

table of conversion character, page 16
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Chapter 1

• 7. printf and scanf (contd)
• printf

Sample Question What is the output? pirntf(8.2f
, 1.234) a)_ _ _ 1.23 b) 1.234 c) _ _ _1.234
d) _ _ _ _ 1.23
d
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Chapter 1

• 7. printf and scanf (contd)
• \n newline

Sample Question include ltstdio.ngt int
main(void) printf(8.2f\n\n\n,
1.234) printf(8.2f\n\n\n, 1) printf( \nd
, 2) return 0 if 1.234 is printed at line
1, which line is 2 written? a)5 b) 7 c) 8 d)6
c
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Chapter 1

• 7. printf and scanf (contd)
• scanf
• Arguments control_string and other_arguments
• control_string conversion specifications
• conversion_character how the data is read?
• c character
• d decimal integer
• f floating-point number
• lf floating-point number (double)
• Lf floating-point number (long double)
• s string
• other_arguments are addresses

table of conversion, page 18
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Chapter 1

• 7. printf and scanf (contd)
• scanf
• Example scanf(d, x)
• address operator
• d how to interpret the input stream
• the input characters typed at the keyboard is
  interpreted as a decimal integer
• x where to store the value
• the value of the decimal integer is stored at the
  address of x.

55
Chapter 1

• 7. printf and scanf (contd)
• scanf

Sample Question Which format should be used to
read a long double value? a) Lf b)lf c)
f d) L
a
56
Chapter 1

• 8. while
• while (expression)
• statement
• statement is executed as long as the value of
  expression is true
• true any non-zero value

57
Chapter 1

• 8. while (contd)

/ Some powers of 2 are printed. / include
ltstdio.hgt int main(void) int e 0,
power_of_two 1 while (e lt 10)
printf("5d", power_of_two 2)
printf("\n") return 0
How many times the body of the loop is executed?
58

• End of Review of
• Chapter 1

59
Chapter 2

• Review Outline
• Comments
• Keywords
• Identifiers
• Constants
• floating numbers
• integer constants

60
Chapter 2

• Review Outline (contd)
• String Constants
• Operators and Punctuators
• Precedence and Associativity of Operators
• Division
• Modulus
• Increment and Decrement Operators
• Assignment Operators
• C System

61
Chapter 2

• Comments
• What is comment?
• Arbitrary strings of symbols placed between the
  delimiters / and /.
• Single line comment // text
• The compiler changes each comment into a single
  blank character.
• Rules
• Multi-line comments cannot be placed in the
  middle of a keyword or identifier.
• Multi-line comments may not be nested.

62
Chapter 2

1. Comments (contd)

Sample Question Which of the following is
correct? a) / comment //a single line comment
/ b) int main(v/ comment/oid) c) int
var/comment/1 d) / comment / comment / /
a
63
Chapter 2

• Keyword
• What is Keywords?
• Keywords are explicitly reserved words that have
  a strict meaning as individual tokens in C.
• Examples of Keywords
• Data Type int, char, long, short
• Keywords cannot be redefined or used in other
  contexts.

The table of keywords, page 46
64
Chapter 2

• Identifier
• What is identifier?
• The names of variables, functions, labels and
  other user-defined items are called identifier.
• Special identifier
• Keywords, names of functions in C library, main
• Rules
• composed of letters, digits, and underscore _ .
• The first character must be a letter or
  underscore.
• case-sensitive
• would not be defined as the special identifiers

65
Chapter 2

1. Identifier (contd)

Sample Question Which of the following is
incorrect? a) int comment b) int _int c) int
int_ d) int 4int
d
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Chapter 2

• Constants
• Floating constants
• float an F suffix
• 1.22F
• double unsuffixed floating constant
• 1.22
• long double an L suffix
• 1.22L
• Character constants
• A

67
Chapter 2

• Constants (contd)
• integer constants decimal, octal, hexadecimal
• Representation of integer constants
• Decimal integer 17
• Octal integer 017
• Hexadecimal integer 0x17
• Conversion between different types
• an octal integer lt-gt a decimal integer
• a hexadecimal integer lt-gt a decimal integer

68
Chapter 2

• Constants (contd)
• A review of binary number
• What is the decimal value of a binary integer?
• A binary integer a ik-1 ik-2 ..i0
• The decimal value is
• ik-1 2k-1 ik-2 2k-2 .. i0 20
• Example
• The decimal value of a binary integer
• a i3i2i1i01101 is
• 1 23 1 22 0 21 1 20 13

69
Chapter 2

• Constants (contd)
• Octal Integer
• What is the decimal value of an octal integer?
• An octal integer a ik-1 ik-2 ..i0
• The decimal value is
• ik-1 8k-1 ik-2 8k-2 .. i0 80
• Example
• The decimal value of an octal integer
• a i3i2i1i07121 is
• 7 83 1 82 2 81 1 80 3665

70
Chapter 2

• Constants (contd)
• Hexadecimal Integer
• What is the decimal value of a hexadecimal
  integer?
• A hexadecimal integer a ik-1 ik-2 ..i0
• The decimal value is
• ik-1 16k-1 ik-2 16k-2 .. i0 160
• Example
• The decimal value of a hexadecimal integer
• a i3i2i1i07121 is
• 7 163 1 162 2 161 1 160 28961

71
Chapter 2

1. Constants (contd)

Sample Question Which of the decimal value of an
octal integer 17? a) 15 b) 17 c) 23 d) 8
a
Sample Question What is the output? print(d,
017) a) 15 b) 17 c) 23 d) 017
a
72
Chapter 2

• String Constants
• String constant is a sequence of characters
  enclosed in a pair of double quote marks.
• Special characters \, \\
• You mustn't split a string constant across lines
• Two string constants that are separated only by
  white space are concatenated by the compiler into
  a single string.

73
Chapter 2

• Operator and Punctuator
• Precedence and Associativity
• determine precisely how expressions are
  evaluated.
• Precedence of operators indicates when they will
  be evaluated.
• Associativity
• left to right Operations are performed from
  left to right
• Examples ,-,/,
• right to left Operations are performed from
  right to left
• Examples (prefix), --(prefix)

74
Chapter 2

• Operator and Punctuator
• Division and Modulus
• Division a/b an integer expression divided by
  another integer expression yields an integer
  value.
• Any fractional part is discarded.
• Modulus ab the remainder after a is divided by
  b.
• If a or b is negative, the results of division
  and modulus are system-dependent
• In a/b and ab, the value of b cannot be zero.

75
Chapter 2

• Operator and Punctuator
• Increment Operator i, i
• Each of the expressions i and i has a value.
• i
• the stored value of i is incremented first
• the expression takes as its value the new stored
  value of i
• i
• the expression takes as its value the current
  stored value of i
• the stored value of i is incremented

76
Chapter 2

• Operator and Punctuator
• Decrement Operator i-- and --i
• Each expression has a value.
• --i
• the stored value of i is decremented by 1
• the expression takes as its value the new stored
  valued of i
• i--
• the expression takes as its value the current
  stored valued of i
• the stored value of i is decremented by 1

77
Chapter 2

• Operator and Punctuator
• Increment and Decrement Operator
• Rules
• Applied to variables but not
• to constants or
• ordinary expressions

78
Chapter 2

• Operator and Punctuator
• Increment and Decrement Operator

Sample Question What is the output? int
i0x11 print(d, i) a) 15 b) 17 c) 23 d)
017
b
79
Chapter 2

• Operator and Punctuator
• Assignment Operator
• op , -, , / , ,
• Semantics
• variable op expression
• equivalent to variable variable op (expression)
• Example
• var expr ? varvar expr
• a 3 ? a a 3
• if a was 4 before the assignment, then a 12
  after that.

80
Chapter 2

• Operator and Punctuator
• Assignment Operator

Sample Question What is the output? int
i0x11 print(d, i 0x11) a) 15 b) 17 c)
34 d) 017
c
81
Chapter 2

• C System
• The C system consists of
• C language,
• The preprocessor
• The compiler
• The library
• Other tools useful to the programmer, such as
  editors and debugger.

82
Chapter 2

• C System (contd)
• C Standard library a collection of header files
  and library files.
• Header file
• The names and characteristics of functions are
  included into computer files called header file.
• Library file
• The actual implementation of functions are
  separated into a library file.

83
Chapter 2

• C System (contd)
• How to use a function in the standard library?
• The programmer needs to provide the function
  prototype.
• Including appropriate header files.
• Do we need to locate the function in the library
  file? No.
• The system knows where to find the code that
  corresponds to functions from the standard
  library.

84

• End of Review of
• Chapter 2