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Lecture 6 & 7

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Lecture 6 & 7

Variables

arithmetic statements

print statements

inputs to the computer

- Assignment 1 due Friday 4pm
- 4th floor engineering building
- no display folders please

- 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

- what is a variable
- types of variables
- arithmetic operations
- PRINT statement
- INPUT and READ and DATA statements

- 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

- 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...

[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

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

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”

DIM x AS LONG

DIM y AS STRING

DIM z AS DOUBLE

DIM zz AS INTEGER

x&

y$

z#

zz%

x%= 3.1234

PRINT x%what type of variable is x%?

x = 3.123456789

PRINT x

- 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

- basic form: PRINT operation (arithmetic)
- PRINT 3 * 2

- PRINT variablelist
- PRINT a, b, c orPRINT x; y; z
- PRINT answer$

- PRINT “prompt”, variablelist
- PRINT “the answer is”, a

- 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

- 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

- 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 radius AS integer

DIM pi AS double

DIM circ AS double

radius = 3.2

pi = 22/7

circ = 2*pi*r

PRINT r,pi,circ

Is this program correct?

- two main ways to get information into the computer
- INPUT statement
- READ and DATA statement

- 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 “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 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 address: "; Address$

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

PRINT "Position envelope in printer and press Enter ."

char% = 1

Temp$ = INPUT$(char%)

LPRINT YourName$: LPRINT Address$

LPRINT CityEtc$

- READ statement assigns variables from corresponding DATA statement
READ variable1, variable2...

.....

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
READ studnumber, names$

DATA 12345, “smith”

- 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?

READ a, b

LET x = a + b

READ a, b

LET y = a * b

RESTORE

READ a, b

LET z = a - b

PRINT x + y + z

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

END

- 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 radius AS integer

DIM pi AS double

DIM circ AS double

radius = 3.2

pi = 22/7

circ = 2*pi*radius

PRINT radius,pi,circ

DIM radius AS integer

DIM pi AS double

DIM circ AS double

radius = 3.2

pi = 22/7

circ = 2*pi*radius

PRINT radius,pi,circ

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

pi = 22/7

INPUT radius

circ = 2*pi*radius

PRINT”radius = “;radius

PRINT”pi = “;pi

PRINT “circumference is“;circ

- 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...

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

READ c, d, e

DATA 2, 4, 1

READ a

DATA b, c, d

PRINT c

DATA 3, 4, 2, 1, 5

END

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

CLS

READ a$, b$, c$

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?

- 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

The End!!