2012年9月26日 星期三

Learning how to communciate with computers - writing C program


In my study,CSCI 1110 (Introduction to Computing using C) is my first programming course.In my secondary school,I did not have any experiences about computer programming.Although I am so worry that C program will be so difficult to me – a beginner of learning programming,I know that equipping good programming skill is very important to a successful engineer.Therefore,I will make effort to study C program in the coming semesterin order to acquire the skill of using C program thoroughly.

Part 1

1.1 Contents of the lectures


In lecture 1, I have learnt some fundamental concepts about computers and programming, including computer organization, computer languages and phases of C programs development.

 
Computer organization:

A computer mainly consists of five component:
(1)   Input unit:
Obtains information from input devicessuch as Keyboard, mouse, microphone, scanner, network.
(2)   Output unit:
Takes information processed by computer and places information on output devices such as screen, printer, networks.
(3)   Central processing unit (CPU):
      CU (Control Units): Supervises and coordinates other      sections of computer
     Arithmetic and logic unit (ALU): Performs arithmetic calculations and logic decisions
(4)   Memory unit:
Rapid access, relatively low capacity warehouse section.
      Retains information from input unit Immediately available for processing.
(5)Secondary storage unit
    Long-term, high-capacity warehouse section.
    Store data and programs that are not immediately needed.
 
 
More about computer organization
 
 
 
 
Computer languages:
 
These five key elements communicate with each other, enabling a computer to operate normally.
Computer languages can be divided into three types:
 
(1)   Machine Languages:
Only language computer directly understands.
Made up of 0s and 1s.
Instruct computers to perform elementary operations.
(2) Assembly Languages:
English-like abbreviations representing elementary computer operations
Easier for humans to read and write.
Incomprehensible to computers, require translator programs (assemblers)to convert to machine language.
(3) High-level Languages:
 
More English-like, use common mathematical notations.
Single statements accomplish substantial tasks.
Translator programs (compilers) convert to machine language.
 
In these languages, high level language is the easieslanguage for humans to understand and edit. Therefore,many modern computer programs are high level language, such as Basic, Pascal, C, C++, C#, Java, Fortran, Perl, Lisp, Cobol, JavaScript.
 
More about these three languages :
 
Phases of C programs development:
The development of C programs includes six phases:
Edit, preprocess, compile, link, load, execute.
 
 
 
In lecture 2, I have learnt the general form of a simple C program,the use of variables,the keywords of C program and the output to the screen.

 
The general form of a simple C program:
The general form of a simple C program is usually :
#include<stdio.h.>
Int main(void)
{ ……
Return(0);
}
This includes a library called “stdio.h” and a main function which contains the main operations to be executed.

 
The use of variables:

 
Variable is a storage cell in the main memory. Itcan be viewed as a box for holding some values. Depending on the type of data it is storing, a variable can occupy one or more bytes.
 
 
The keywords of C program:

 
Keyword is a word that has a strict meaning.It cannot be redefined or used in other ways.C program has 32 keywords.
 
The output to the screen:

 
The statement–printf(“…”); is used to give a command of output to the screen.
For example,
 
 
 
The above program output the sentence “Hello, world!” and “Hello, universe!” by two printfstatements.

 
1.2 Learning Process:

 
As a beginner of C program, it is important for me to spend more time on preparation and practices in order to learn it efficiently.Before the lecture,I would read the whole lecture note one time to have a better understanding in the lecture.When I meet difficultproblem,I would mark it down so that I can pay more attention on this part during lecture.
 
 
Moreover, in order to get more information for learning,I borrowed a book about C programming,called C : how to program.It is a guidebook for C program beginner.It introduces how to write C program step by step with example. I think this reference book is very helpful for me to learn how to write C program.

 
Moreover,I think the best way for beginner to learn C program is to practice more.

 
In order to do so,I have installed Microsoft Visual Studio 2012 in my computer and tried to do the C program exercises at the tutorials and reference book.This gave me opportunities to apply the knowledge learnt from the lesson into real applications.

 
Part 2
 
A interesting topic in the lesson –output statement

 
A brief description about the topics :

 
As mentioned before,The statementprintf(“…”); is used to give a command of output to the screen.

 
The below code is the printf example at the lecture note:
 

 
The above program output the sentence “Hello, world!” and “Hello, universe!” by two printfstatements.

 
My opinion, commends, ideas, and further information about output statement :

 
After seeing the above example at the lecture note,I have two problems in my mind.

 
First,can I use one printf statement to output the two sentences instead of using two printf statements?
 
 
 
After my testing,I find that if I add write the statement printf (”sentence1\nsentence2”);  , I can print two sentences in different line.

 
I think my method is better than the method in the lecrture note.It is because my method can reduce the number of statements written in the program and therefore make the whole program run faster.From this example,I understand that knowledge in the lecture or book is not the only correct answer.If we are willing to think more critically,we may find some better solution.

 
The second problem in my mind is that can a C program display characters/strings that are input by user?After surfingthe wensite,I find that it can be done by using a scanf statement before a printf statement.
 
 


Website about scanf and printf :

 
http://caterpillar.onlyfun.net/Gossip/CGossip/PrintfScanf.html

 
I think this application is very useful and important in our real life.For example,Automated Teller Machine (ATM) may ask customer to enter amount of money they want to take by scanf and display the amount of money on the screen by printf.
 
 

 
From this example,I understanding that program is essential in our daily life.To be a good information engineer,I must acquire the skill of using C program thoroughly,

 
In the coming lecture,I will learn more advanced knowledge about C program.I will continue to make effort on writing C program and hope that I can acquirea good skill of writing C program at the end of this semester.


 
 

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