chapter 1 basic programming concepts

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OBJECTIVES:

At the end of this chapter the students should be able to:

1. Define a computer program.

2. Identify a programming language.3. Differentiate the types of programming languages.

4. Discuss the evolution of the C++ programming

language.

5. Identify an algorithm and its methods of

representation.

6. Write algorithms through flowcharting.

CHAPTER 1BASIC

PROGRAMMING

CONCEPTS


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Welcome to C++. But before we explore the beauty of C++ programming, let us

first discuss the basic concepts of programming.

1.1 Programming Languages

A program is a set of instructions that tells the computer what to do. In writing

such instructions, a programmer, a person who writes programs, needs a third party

between him and the computer, a programming language. There are two types of

programming languages: low-level languages and high-level languages.

Low-level languages require programmers to have a good understanding of the

underlying hardware. Two different and incompatible processors understand only

its own low-level language making it machine dependent. Low-level languages

include machine languages and assembly language. Machine languages are at the

lowest level defined by a combination of circuits that can either be on or offrepresented by binary numbers 1 and 0, respectively. Assembly language iscomposed of instruction codes stated in mnemonic forms (ADD for add, SUB for

subtract, etc.). To convert these program codes into machine language codes, an

assembleris being used.

High-level languages are the more convenient programming language mainly

because they are quasi-English and do not require the programmer to know the

actual computer hardware. These languages use either a compileror an interpreter

to run programs. Compilers translate human readable programs in to machine

language before they can be executed, while an interpreterprogram executes high-

level language programs directly without the need for compilation. High-level

languages include:

FORTRAN FORmula TRANslator

COBOL COmmon Business-Oriented Language

PL/1 Programming Language 1

BASIC Beginners All-purpose Symbolic Instruction Code

Pascal

C & C++

Java

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1.2 The Evolution of the C++ Programming Language

C++ is an extension of the C programming language, which acquired its ideas fromBCPL and B.

BCPL and B are typeless languages, compared with C and C++ which provides

a variety of data types. Martin Richards developed BCPL in 1967 whose objective

is for operating systems and compilers development. Using a DEC PDP-7

computer, Ken Thomson developed B in 1970 at the Bell Laboratories. It was thenused to create early versions of the UNIX operating system.

From B comes C, which was developed in 1972 by Dennis Ritchie also at Bell

Laboratories using a DEC PDP-11 computer. Not until the publication of The C

Programming Language book by Kernighan and Ritchie himself in 1978, has the

language became very popular. In addition to its gaining popularity during thosetimes, the American National Standard Institute (ANSI) moved for the

standardization of C (ANSI C) in 1983, and was later approved late in 1988.

Modern compilers support this standardization.

In 1990, Bjarne Stroustrup developed C++ also at Bell Laboratories. Evolving

from the C language, C++ provides capabilities for object-oriented programming.

However, being a hybrid language, C++ allows C-like programming (i.e.

structured), object-oriented programming, or both.

1.3 ALGORITHMS

An algorithm is a well-defined procedure that takes some value (or set of values)

as input and produces some value (or set of values) as output. It can also be

defined as a set of instructions, which if followed, accomplish a particular task.

Some of the advantages in writing algorithms before actual program coding are as

follows:

1. Algorithms are language independent.

2. Problems can be analyzed and interpreted in a more efficient way.

3. Algorithms can serve as a guide during system development, debugging

and analysis.4. Program maintenance becomes easier.

5. Algorithms help in program documentation.

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However, there are also some disadvantages, such as:

1. Given a complex problem at hand, the algorithm can be equally

complicated.2. There are cases where the algorithm needs to be rewritten completely.

For an algorithm to be suitable for computer use, it must possess the following

criteria:

1. Input: Zero or more quantities are externally supplied.

2. Output: At least one quantity is produced.

3. Definiteness: Each instruction must be clear and unambiguous.

4. Finiteness: The algorithm must terminate after performing a finite numberof steps

5. Effectiveness: Both the criteria of definiteness and effectiveness must be

satisfied wherein every instruction must be sufficiently basic that it can becarried out.

There are two common methods of representing an algorithm: pseudocode and

flowchart. A pseudocode is an algorithm presented in an informal language. A

flowchart is a diagram or a blueprint that shows a sequence of operations to be

performed in solving a computational problem.

1.4 FLOWCHARTS

In this section, we will be presenting algorithms using flowcharts rather thanpseudocodes. Flowcharts are more preferred for introduction due to its simplicity,

with pseudocodes for advanced users.

There are two types of flowcharts: system and program flowchart. A system

flowchart defines the major phases of a particular processing system, as well as the

various media used. A program flowchart shows a sequence of operations the

computer is to perform to solve a specific programming problem. The latter will be

the focus of the discussion of this book.

ANSI defined a set of standard flowcharting symbols presented in Figure 1.1.

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Figure 1.1

Common Flowcharting Symbols

The Terminal SymbolThis symbol indicates the start and end of a flowchart. It

usually contains the word START or END.

The Input/Output Symbol This symbol indicates that some form of input or

output is performed.

The Process Symbol Drawn with a rectangle, this box an shows action or

processing of operations.

The Decision/Branching Symbol This diamond symbol shows that a branch to

one of two or three options is possible.

The On-Page Connector This symbol is used to connect a part of a flowchart to

another situated on the same page. It uses a common identifier, such as a letter,

showing the exit and entry point of the flowchart.

The Off-Page Connector This symbol is used to connect a part of a flowchart to

another situated on another page. Like the on-page connector, it uses a common

identifier showing the exit and entry point of the flowchart.

The Preparation Symbol This hexagonal symbol is normally used for

initialization.

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The Flowline Symbols These arrowhead lines indicates a direction of flow or

sequence of flowchart operation.

In writing or designing flowcharts, it is important to follow certain guidelines.

These are as follows:

1. List all necessary requirements in a logical order.

2. Ensure that the flowchart starts and ends with a terminal symbol.

3. The flowchart must be unambiguously presented.

a. Only one flow line is used with a terminal symbol.

b. Only one flow line should come out from a process symbol.

c. Only one flow line should enter a decision symbol, with two or

three flow lines coming out of it.

The flow of the procedure must normally be presented from left to right

or top to bottom.

4. The description of a computational process or a data must be written

briefly, but clearly.5. Use connector symbols when the flowchart becomes complex to avoid

intersection of flow lines.6. Test the flowchart using some simple test data.

Flowchart 1.1 shows a very simple example of a program flowchart.

Start

End

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Flowchart 1.1

Sample Flowchart that Prints Welcome to Flowcharting

Flowchart 1.1 has three flowcharting symbols: terminal, flowline, and

input/output. It starts with a terminal symbol signifying the START of theflowchart. A flowline from the START flows to an input/output symbol, which

indicates that Welcome to Flowcharting will be printed, and finally a flowline to

another terminal symbol to show the end of the flowchart.

1.4.1 Basic Operators

Since this section is a preliminary to program development in C++ we will beusing the same set of operators that C++ uses in manipulating data. Table 1.1

shows a summary of the basic operators we will use in writing flowcharts:

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Operator Operation Description

+ arithmetic ADDITION returns the sum

- arithmetic SUBTRACTION returns the difference

* arithmetic MULTIPLICATION returns the product/ arithmetic DIVISION returns the quotient

% arithmetic MODULO returns the remainder in

arithmetic division

== relational EQUAL TO returns TRUE if the left operand

is equal to the right operand,otherwise returns FALSE

!= relational NOT EQUAL TO returns TRUE if the left operand

is not equal to the right operand,

otherwise returns FALSE

< relational LESS THAN returns TRUE if the left operand

is less than the right operand,


> relational GREATER THAN returns TRUE if the left operand

is greater than the right operand,


= relational GREATER THAN

OR EQUAL TO

returns TRUE if the left operand

is greater than or equal to theright operand, otherwise returns

FALSE

|| logical OR returns FALSE if both the left and

right operands are FALSE,

otherwise returns TRUE

&& logical AND returns TRUE if both the left and

right operands are TRUE,


! logical NOT returns TRUE if the right operand

is FALSE, otherwise returns

FALSE.

= assignment assigns a right hand value to a left

hand variable

( ) grouping symbol groups a set of operationsTable 1.1

Basic Operators

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1.4.2 Basic Flowcharting Patterns

The following are flowcharting patterns that we will discuss in this section:

1. Sequential Pattern The flow executes in sequence.

For example, write a program that will read in two numbers and output

their sum and average.

Flowchart 1.2Sample Sequential Pattern

The first process involves a terminal symbol indicating the start of

flowchart. We then read in (input) two numbers and store them to

variables NUM1 and NUM2.

Next are processes involving two operations, i.e., addition and division.

The first process involves the adding of the two variables and storing the

result into the variable SUM, which was then divided by 2 and was storedinto the variable AVERAGE.

We will then output (write) the results, i.e., the contents of SUM and

AVERAGE, and finally terminate the flowchart with the end terminalsymbol.

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2. Selection Pattern The execution flow depends on a certain

condition. This condition normally involves an operation that may

result to either TRUE or FALSE.

For example, write a program that will read in an integer and output

the word POSITIVE if it is a positive integer, and NEGATIVE if

otherwise.

Flowchart 1.3

Sample Selection Flowchart

Just like our first example, we start and end our flowchart with a terminal

symbol. However, the flowchart above allows the flowchart to decide

whether to output the word POSITIVE or NEGATIVE depending on the

result of the decision or branching symbol, i.e. if INTEGER is greater than

or equal to 0 - output POSITIVE, otherwise - output NEGATIVE.

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3. Loop Pattern The execution flow is performed a certain number

of times depending on some condition.

For example, draw a flowchart that will print the numbers 1-10.

Flowchart 1.4

Sample Loop Pattern

In the example above, we initialize a variable NUM to 1. We output this

value using a input/output symbol. The next step, i.e., NUM=NUM+1, isa shorthand process that increments the value of NUM by 1, which meansadd 1 to the current value of NUM (in the first case 1+1 = 2), and assign

this value to NUM.

The next step is to test whether NUM is greater than 10. If this condition

is true, we then execute the terminal symbol END. Otherwise, we move to

the on-page connector symbol that instructs the flowchart to move to the

location pointed to by the connector. This is the part that illustrates a loop

pattern.

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SUMMARY

In this chapter we discussed the basics of computer programming: define a

program, know what programming languages are, what are its types. C++ being

the focus was described briefly by stating how the programming language evolved.

Algorithm development was introduced thru flowcharting to develop the logical

thinking of the students.

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PRACTICE EXERCISE #1

NAME: __________________________ DATE: ____________________

COURSE/YR-SEC: ________________ INSTRUCTOR: ____________

DIRECTION: Draw a flowchart that will perform the following instructions.

1. Input an integer. Print DIVISIBLE if the number is divisible by 2,

otherwise, print NOT DIVISIBLE.

2. Input three numbers and print only the highest number.

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NAME: __________________________ DATE: ____________________

COURSE/YR-SEC: ________________ INSTRUCTOR:_____________

3. Input three numbers and output the numbers in ascending order.

4. Print the odd numbers from 99 to 1.

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NAME: __________________________ DATE: ____________________


5. Print the numbers divisible by 5 from 10 to 1000.

6. Print the numbers divisible by three but not divisible by 9 from 3 to 99.

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NAME: __________________________ DATE: ____________________


7. Print the following series of numbers: 1, 1, 2, 3, 5, , 89.

8. A triangle is equilateral if all three sides are equal, isosceles if only two of

its sides have the same length and scalene if no two sides have the same

length. Draw a flowchart to input the lengths of the three sides of a

triangle and print whether the triangle is equilateral, isosceles or scalene.

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NAME: __________________________ DATE: ____________________


9. A young man agrees to work for a company at a very modest salary of

P100.00 per week with a condition that his salary will double each week.

How much is his weekly salary and earnings at the end of six months

(assume that each that there are four weeks per month).

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10. The cost of a certain item depends on a quantity ordered as given by the

following table:

QUANTITY ORDERED COST/ITEM1-99 P 5.95

100-199 5.75

200-299 5.50

300 or more 5.10

Draw a flowchart to input the quantity ordered and output the total cost.

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chapter 1 basic programming concepts

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