Upload
lemonmichelangelo
View
48
Download
0
Tags:
Embed Size (px)
Citation preview
QBasic and QBasic and Programming Programming PresentationPresentation
Prepared by:Obusan, Janssen Roselle T.
Opiana, Christian Joseph I.
QBasic
It all started back in 1963 when John Goerge Kemeny and Tom Kurtzas got together at Dartmouth College.
It is an interpreter which reads every line, translates it and lets the computer execute it.
NOTE: BASIC stands for Beginner’s All Purpose Instruction Code.
RulesRules and Its and Its FeatureFeature
QBasic programs are executed in the order which they are written.
Every statement should have at
least one QBasic command.
All commands have to be written using the Syntax Rules. Syntax is the grammar of
writing.
It is a user friendly
language.
It is widely known and accepted
programming language.
It is one of the most flexible languages, as
modification can easily be done.
Language is easy since the
variables can be named easily
and uses simple English phrases.
DataData(A collection of facts and figures that is entered into the (A collection of facts and figures that is entered into the
computer.)computer.)
CONSTANTCONSTANT
(Data whose values do not change)
Numeric Constant(numbers – negative or positive – used for mathematics)
e.g. 100
Alphanumeric Constant/String(numbers of alphabets written within double quoutes)
e.g. “computer”
VARIABLEVARIABLE
(Data whose values can change fue to some calculation)
Numeric Variable(numbers that are constant for arithmetic)
e.g. A = 50
Alphanumeric Variable(variable that holds an Alphanumeric constant)
e.g. Name$ = “Akanksha”
Modes Modes (QBasic can be made to translate your instructions in two (QBasic can be made to translate your instructions in two
modes.)modes.)
Direct
Mode
Program
Mode
Accepts single line instructions from the user and the output is viewed as soon as the key is pressed.
This mode is used to types a program which is stored in the memory. They have line numbers. We have to give the command to get the output.
Note: Every programming language has its own SYNTAX (rules) and COMMANDS.
Keywords and their FunctionsKeywords and their Functions
LISTUsed to list
the programs on the screen.
RUNUsed to
execute the program.
LLISTUsed to list the program
as a hardcopy.
LPRINTUsed to get the output of the
program on the hard copy.
NEWUsed to clear the
memory of a existing program.
Keywords and their FunctionsKeywords and their Functions
SYSTEMUsed to take you back to dos prompt.
PRINT & CLSPrint is used to
display on screen.CLS is used to
clear the screen.
RMEUsed to show the position of the mistake.
SAVEUsed to save the program.
LOADUsed to load the
program from the disk to the memory.
QBasic CommandsQBasic Commands
CLS
This command is used to clear the screen.
This command is used to display the output on the screen.
REM
It stands for ‘remark’. It makes the program
more understandable to the reader.
LET
It assigns a value to a variable in a program.
NOTE: A numeric data should be assigned to a numeric variable and aplhanumeric data to an alphanumeric variable.
QBasic CommandsQBasic Commands
END
This command is usually given at the end of the program.
INPUT
It allows the user to enter a value for the variable while running the program.
DELETE
To delete a line number in a program.
QBasic Reminders!QBasic Reminders!
A program consists of a line
number.
It contains keywords like:
PRINT, END etc.
Each program line begins with
positive number.
Run is used to execute a program.
It is possible to overwrite a statement but if you want to write a new program, use the
NEW command.
To exit the QBasic program, SYSTEM command is used.
NO TWO LINES
SHOULD HAVE SAME NUMBER.
When the PRINT command, When the PRINT command, you can also print you can also print NUMBERS to the screen. NUMBERS to the screen. Delete the current Delete the current program (unless you program (unless you already have) and write already have) and write the following:the following:
PRINT 512 (or ?512)PRINT 512 (or ?512)
<press enter><press enter>
Press F5 to run the Press F5 to run the program. The program program. The program outputs: outputs:
512512
COMMANDSCOMMANDS
There are also special There are also special functions called functions called “COMMANDS” (also “COMMANDS” (also called called “INSTRUCTIONS”). A “INSTRUCTIONS”). A “COMMAND” tells the “COMMAND” tells the QBASIC interpreter to QBASIC interpreter to do something.do something.
The PRINT command The PRINT command tells the QBASIC tells the QBASIC interpreter to print interpreter to print something on the something on the screen. In this case, screen. In this case, the interpreter printed the interpreter printed “HELLO WORLD!”.“HELLO WORLD!”.
TIP: Instead of typing
PRINT, you can enter a
question mark. For
example:
?“HELLO WORLD!”
EXPRESSIONSEXPRESSIONS
An expression is something the An expression is something the interpreter calculates (or evaluates). interpreter calculates (or evaluates). Such as:Such as:
1+11+1 (returns 2)(returns 2)100-147100-147 (returns 53)(returns 53)3*343*34 (returns102)(returns102)80/480/4 (returns 20)(returns 20)(100*3)+56(100*3)+56 (returns 356)(returns 356)
If you pass an expression to the PRINT command, the value
returned (a number) is printed.
Clear the current program and then run the following:
PRINT 512+478
PROGRAM OUTPUT:990
if you enclose the expression with quotation marks, the expression becomes a string and isn’t evaluated. For example:
PRINT “512+478OUTPUT512+478
ACTIVITYACTIVITY
1.1. EVALUATE:EVALUATE:
A.A. 14/2-3*1=14/2-3*1=
B.B. 8*2/(5-1)=8*2/(5-1)=
C.C. 3+5^2*4=3+5^2*4=
D.D. 4+(3*2-1)^2/5=4+(3*2-1)^2/5=
ACTIVITY(Continuation)ACTIVITY(Continuation)
2. EXPRESS IN INTEGER OR DECIMAL 2. EXPRESS IN INTEGER OR DECIMAL FORMFORM
A.A.5.0D+7=5.0D+7=
B.B.-1.23D+03=-1.23D+03=
C.C.1.234D-04=1.234D-04=
D.D.4.26305D+084.26305D+08
RETRIEVING KEYBOARD RETRIEVING KEYBOARD INPUT FROM THE USERINPUT FROM THE USER
One way to receive input from the keyboard is with the INPUT command. The INPUT command allows the user to enter either a string or a number, which is then stored in a variable.INPUT data$PRINT data $
When is the program executed, the INPUT command displays a question mark, followed by a
blinking cursor. And when you enter text, the program stores that text into the variable data$, which
is printed to the screen.
TIP: if you place a string and a semi-colon between INPUT and the variable, the program will print the string.INPUT “ENTER SOME TEXT:”; data$
To receive a number, use To receive a number, use a non-string variable.a non-string variable.
INPUT numberINPUT number
PRINT numberPRINT number
If you enter text instead If you enter text instead of a number, the QBASIC of a number, the QBASIC interpreter displays an interpreter displays an error message (“Redo error message (“Redo from start”).from start”).
RETRIEVING KEYBOARD RETRIEVING KEYBOARD INPUT FROM THE USERINPUT FROM THE USER
Below is another example of the INPUT command:
PRINT “Enter some text:”INPUT text$
PRINT “Now enter a number:”
INPUT numPRINT text$PRINT num
THE IF AND THEN COMMANDS
The IF and THEN commands are used to compare an expression and then perform some task based on that expression.X=5IF X=5 THEN PRINT “ X equals 5”Since X does equal 5 in this case, the program outputs:
X equals 5
EXPRESSION SIGNSYou can also enter the following statements, instead of the equals sign:X<5 (x is less than 5)X>5 (x is greater than 5)Run the following: X=16IF(X>5) THEN PRINT “X is greater than 5”
THE IF AND THEN THE IF AND THEN COMMANDSCOMMANDS
You can also combine the signs like this:
x<=5 (x is less than or equal to 5)
X>=5 (x is greater than or equal to 5)
X<>5 (x does not equal to 5)
Run the following example:
CLSX=5
IF (X>=5) THEN PRINT “X is greater than equal to
5”IF (X<=5) THEN PRINT “X is less than or equal to 5”IF (X<>5) THEN PRINT “X
does not equal to 5”OUTPUT:
X is greater than or equal to 5
X is less than or equal to 5
ELSEELSE Using the ELSE command, you can
have the program perform a different action if the statement is
false.x=3
IF x=5 THEN PRINT “Yes” ELSE PRINT “No”
Since X doesn’t equal to 5, the output is:
No
END IF
END IF allows you to have multiple commands after the IF… THEN statement, but they must
start on the line after the IF statement. END IF should appear right after the list of commands.
Prepared by:Prepared by:Obusan, Janssen Roselle T.Obusan, Janssen Roselle T.Opiana, Christian Joseph I.Opiana, Christian Joseph I.