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# Lecture 6 & 7 PowerPoint PPT Presentation

Lecture 6 & 7. Variables arithmetic statements print statements inputs to the computer. Notices. Assignment 1 due Friday 4pm 4th floor engineering building no display folders please CMA’s submit anytime Thursday Show holiday - PALs makeup. Readings & activities.

Lecture 6 & 7

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## Lecture 6 & 7

Variables

arithmetic statements

print statements

inputs to the computer

### Notices

• Assignment 1 due Friday 4pm

• 4th floor engineering building

• CMA’s submit anytime

• Thursday Show holiday - PALs makeup

• Study Book; Module 8 & 9 note error in summary of readings handout

• Qbasic with an Intro to Visual Basic by Schneider; p40 to 47; p55 to 57

• Practice Problems and Exercises 3.1 & 3.2 as necessary

• Schneider pp 59 - 66

• exercies 3.3 p 67 - as required

• Schneider p 69 #’s 17, 20, 21, 25

### This lecture

• what is a variable

• types of variables

• arithmetic operations

• PRINT statement

• INPUT and READ and DATA statements

### Variables - revision

• Quantities referred to by symbolic names

• make general solutions

• Variable name: is the name of a storage location in primary memory where Qbasic stores the value of the variable

• value can change during program execution

### Variable names

• may only contain letters, digits and full stop

• may not contain a blank space

• must start with a letter and may be up to 40 characters

• may NOT be a reserved word e.g let, print

• generally given a value of 0 initially but...

### Assigning variables

[LET] variablename = variable

• e.g.

LET x = 2

x = 2

LET sum = 24

sum = 24

LET counter = counter +1

total = total + x

}

}

x = 2

y = 3 * x

x = y + 5

PRINT x + 4

y = y + 1

END

xy

2

6

11

OUTPUT - 15

7

### Determine variables and outputs

single-precision

default type

double-precision

scientific notation for printing very large or very small numbers

integer

long-integer

string

-3.37*1038to 3.37* 1038

-1.67 *10308to 1.67* 10308

1 * 10-5 = 1E-5

.000013596426 = 1.359643E-5

-32 768 to 32 767

-2 147 483 648 to 2 147 483 648

any alphanumeric

### Types of Variables

TYPE statement e.g.

DIM x AS integer

DIM variablename AS type

Types

single

double

integer

long

string

Suffix on variable name

! (Single)

# (Double)

% (Integer )

& (Long)

\$ (String)

single precision

integer

double precision

string variable

total = 6

total% = 6

total# = 6

total\$ = “6”

### Determine types of variables

DIM x AS LONG

DIM y AS STRING

DIM z AS DOUBLE

DIM zz AS INTEGER

x&

y\$

z#

zz%

### Output of Program?

x%= 3.1234

PRINT x%what type of variable is x%?

x = 3.123456789

PRINT x

### Arithmetic Operations

• five arithmetic operations

• additions (+); subtraction (-); division(/); multiplication (*); exponentiation (^)

• executed in a specific order

• ( ) inner to outer; left to right

• ^ left to right

• * and /; \ (integer division); MOD (modulus); left to right

• + and - ; left to right

### PRINT statement

• basic form: PRINT operation (arithmetic)

• PRINT 3 * 2

• PRINT variablelist

• PRINT a, b, c orPRINT x; y; z

• PRINT “prompt”, variablelist

• PRINT “the answer is”, a

### Screen Placement & Formatting

• PRINT zones

• line has 80 characters

• subdivided into 5 zones

• zones 1 - 4 have 14 characters

• zone 5 has 24 characters

• zones start at columns 1, 15, 29, 43 & 57

### Print zones contd

• commas as separators in PRINT statement

• next item printed in next zone

• statement ends in comma

• next item printed in next print zone

• semicolon as separators in PRINT statement

• separated by 2 spaces

• statement ends in semicolon

• next item separated by 2 spaces

### Problem

• draw a flowchart which will

• define variables for pi, radius and circumference as double, integer and double respectively

• set radius = 3.2, pi = 22/7

• calculate the circumference

• print all variables

### Flowchart

DIM pi AS double

DIM circ AS double

pi = 22/7

circ = 2*pi*r

PRINT r,pi,circ

Is this program correct?

### Inputs to the computer

• two main ways to get information into the computer

• INPUT statement

### INPUT - simplest form

• INPUT variable1, variable2....

EXAMPLES:

INPUT x

INPUT studnumber, names\$

• program stops and waits for user to enter variables

• number and type of variables must match

### INPUT with prompt

• INPUT “prompt”; variablelist

INPUT “enter values for a and b”; a, b

enter values for a and b? 1,2

INPUT “enter values for a and b”, a, b

enter values for a and b1,2

• variablelist separated by commas

• user input must match in type and number, separated by commas

### Input statement

• INPUT reads input from the keyboard or a file.

• LINE INPUT reads a line of up to 255 characters from the keyboard or a file.

• INPUT [;] ["prompt"{; | ,}] variablelist

• LINE INPUT [;] ["prompt";] variable\$

• INPUT\$(n[,[#]filenumber%])

CLS

PRINT "This is a program to print envelopes."

PRINT "Press any key when you are ready to begin ..."

Temp\$ = INPUT\$(1) 'Assign value to variable

LINE INPUT "Enter your name: "; YourName\$

LINE INPUT "Enter your city, state, and ZIP code: "; CityEtc\$

PRINT "Position envelope in printer and press Enter ."

char% = 1

Temp\$ = INPUT\$(char%)

LPRINT CityEtc\$

• READ statement assigns variables from corresponding DATA statement

.....

DATA data1, data2...

variable1 = data1; variable2 = data2 etc

• following READ statements continue from data list

• cannot ‘run out’ of data - OUT OF DATA ERROR

• variable types must match

DATA 12345, “smith”

### Restore statement

• Restores data pointer to start of data

• next READ assigns from first DATA statement, first variable

What will be displayed when the following program is executed?

LET x = a + b

LET y = a * b

RESTORE

LET z = a - b

PRINT x + y + z

DATA 2, 4, 3, 1, 5, 3

END

### Problem

• draw a flowchart which will

• define variables for pi, radius and circumference as double, integer and double respectively

• set radius = 3.2, pi = 22/7

• calculate the circumference

• print all variables

DIM pi AS double

DIM circ AS double

pi = 22/7

### Program - general solution?

DIM pi AS double

DIM circ AS double

pi = 22/7

DIM radius AS integer, pi AS double, circ AS double

pi = 22/7

PRINT”pi = “;pi

PRINT “circumference is“;circ

### Now change the program to include INPUT statements

• Draw a flowchart that take two times in hours, minutes and seconds and will calculate the total time in hours minutes and seconds e.g 2 hr, 15 min & 12 sec + 1 hr 10 min and 5 sec = 3 hrs 25 min and 17 sec

## The End

Tutorial to follow...

### TUTORIAL

1. Which is the correct hierarchy for arithmetic operators (from those evaluated first to those evaluated last).

2. What value will be assigned to x when the following statement is executed?

LET x = 4 * 3^2 / 5 * 4

3. The following statement is valid. (T/F)

INPUT "IS THIS OK"; q

4. The following statement is valid. (T/F)

DATA 25, "X + 16", 14

5. The following statement is valid. (T/F)

INPUT x, 5

6. What will be displayed when the following program is executed?

DATA 5, 3

DATA 2, 4, 1

DATA b, c, d

PRINT c

DATA 3, 4, 2, 1, 5

END

7. What will be the output of the following program?

CLS

PRINT a\$, b\$, c\$, b\$

DATA The, best, "of the"

END

7. Evaluate the following numeric expressions.

(a) 2 - (1 - 1)

(b) 12 / 4 + 3 * 2

(c) 2 + 9 * 2

(d) 10 - 3 ^ 2

(e) How would you modify the expression in (d) without changing any of the numbers so that it evaluates to 49?

### Problem

• Suppose a ball is thrown straight up in the air with an initial velocity of 50 m/s. How high will the ball be after t seconds given that:

ht = -16t2+ v0t + h0

where ht is height after t seconds; v0 is initial velocity and h0 is initial height