Introduction to computer programming

Introduction to
Computer
Programming
Lanie P. Plecerda
Instructor I

Computer program
- is a list of instructions that the computer
machine follows to properly accept input,
correctly process them and present the results
in the most understandable way.
Computer Programming
– is considered to be an art and at the same time a science. It is an art because
there is no standard way to interpret a problem and solve it using a standard form of
programming procedures and styles. It is fast becoming a science because standard
programming practice is starting to be adopted.

Programs fall into two major classes:
application programs and operating
systems. An application program is
one that carries out some function directly
for a user, such as word processing or
game-playing. An operating system is a
program that manages the computer and
the various resources and devices
connected to it, such as RAM (random
access memory), hard drives, monitors,
keyboards, printers, and modems, so that
they may be used by other programs.

A programmer uses another type of program
called a text editor to write the new program
in a special notation called a programming
language. With the text editor, the
programmer creates a text file, which is an
ordered list of instructions, also called the
program source file. The individual instructions
that make up the program source file are
called source code. At this point, a special
applications program translates the
source code into machine language, or
object code — a format that the operating
system will recognize as a proper program and
be able to execute.

Three types of applications programs
translate from source code to object
code: compilers, interpreters, and
assemblers. The three operate differently
and on different types of programming
languages, but they serve the same
purpose of translating from a
programming language into machine
language. A compiler translates text
files written in a high-level programming
language—such as Fortran, C, or Pascal—
from the source code to the object code
all at once

Computer is composed of:
1. CPU (Central Processing Unit) –
this is where all mathematical and logical
forms of processing are done on data.
2. Memory – before a computer can do
any productive work such as
programming, it has to remember things
such as data it needs to produce
information.

3. Input and Output Device – data
have to come into the computer by first
entering them through input devices.
Ex. Keyboard. After the computer
executes a program to process data
and produce information, this
information remains in the memory.
Part of the program has to show these
results to the outside world. Output
devices such as monitor screen and
printers are used to display the results
to the user.

4. Software – computers today come
bundled with some software already
installed in them.
Operating System – performs for the
programmer many tasks that used to
be very difficult to program

Two forms of Memory
• Internal memory (RAM-Random
Access Memory) – stores programs and
data that are executed and processed by
the computer.
• Secondary memory – supplements RAM
so those computers are able to
permanently save programs and data that
are not yet needed for execution and
processing. Ex. Floppy disk, hard disk &
etc.

The following are standard Operating
System functions.
•Validating user identification
every time the user uses the
computer
•Provides standard functions like
editor, compilers and linkers
•Manages files of the user by
providing functions like Copy,
Delete, Append

The following are standard Operating
System functions.
•Retrieves data out of data files
•Manages memory for the user by
determining where in the memory a
program is to be loaded every time it is
called to run
•Makes communication between the CPU,
Memory and input/output devices
transparent to the user or the user are
unaware of these things while they are at
work.

High level languages
– are programming languages that
are closer to human language than
to machine language. They are
characterized to use common
English words as their instructions.
Aside from that, high level
languages have the following
characteristics:

High level languages
• Requires additional step of compilation or
translation so that from high-level, another
program that has exactly the same meaning
and intended results in low-level or machine
language can be generated and loaded into
the computer and executed.
• A compiled program is usually not as
efficient as when the program was originally
written in machine language or assembly.
This is due to the fact that compilers add a
lot of extra overheads in terms of memory
and non-optimized logical translations.

Each of these programming languages
was designed to solve particular kinds
of problems.
• COBOL – Common Business Oriented Language was
designed to solve business problems like accounting.
• FORTRAN – Formula Translation is a high level
language used for scientific and engineering
applications.
• Pascal and C – are general-purpose language. They
are high-level language but they can be embedded
with assembly language code effectively making these
languages middle-level languages. C language is
responsible in the implementation f major software
including operating systems, compilers and software
development tools.

The Simplest computer
programs perform three basic
operations:
• get the input from the keyboard
• process the input data
• display the results on the screen
INPUT DATA
PROCESS DATA
DISPLAY ALL RESULTS

The most basic form of a C program
follows a very simple format:
pre-processor
directives
main function
{
declarations
statements
}

First Example
/*Converts weight in pounds to kilograms*/
#include <stdio.h>
#define kg_in_pound .454
int main()
{float pounds, kilograms; /*declare both weights as float data type*/
printf(“Enter weight in pounds :”)
scanf(“%f”,&pounds);
kilograms = kg_in_pound * pounds;
printf(“5.2f Pounds is equal %.2f kilograms,n”, pounds, kilograms);
getch();
return(0);
}

Introduction to computer programming

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Introduction to computer programming