Operators Identifiers The Data Elements Arithmetic Operators exponentiation

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Operators & Identifiers The Data Elements

Operators & Identifiers The Data Elements

Arithmetic Operators • • exponentiation multiplication division (real) division (integer quotient) division (integer remainder)

Arithmetic Operators • • exponentiation multiplication division (real) division (integer quotient) division (integer remainder) addition Subtraction assignment ^ * / Mod + =

Evaluate these expressions = 100 / 10 / 5 = 100 / 10

Evaluate these expressions = 100 / 10 / 5 = 100 / 10 5 = 100 10 / 5 = 100 + 10 Mod 5 = 100 + 10 5

Evaluate these expressions = 100 / 10 / 5 = 100 / 10

Evaluate these expressions = 100 / 10 / 5 = 100 / 10 5 = 100 10 / 5 = 100 + 10 Mod 5 = 100 + 10 5 2

Evaluate these expressions = 100 / 10 / 5 2 = 100 / 10

Evaluate these expressions = 100 / 10 / 5 2 = 100 / 10 5 = 100 10 / 5 = 100 + 10 Mod 5 = 100 + 10 5 2

Evaluate these expressions = 100 / 10 / 5 = 100 / 10

Evaluate these expressions = 100 / 10 / 5 = 100 / 10 5 = 100 10 / 5 = 100 + 10 Mod 5 = 100 + 10 5 2 2 50

Evaluate these expressions = 100 / 10 / 5 = 100 / 10

Evaluate these expressions = 100 / 10 / 5 = 100 / 10 5 = 100 10 / 5 = 100 + 10 Mod 5 = 100 + 10 5 2 2 50 100

Evaluate these expressions = 100 / 10 / 5 = 100 / 10

Evaluate these expressions = 100 / 10 / 5 = 100 / 10 5 = 100 10 / 5 = 100 + 10 Mod 5 = 100 + 10 5 2 2 50 102

Variables • A variable is a string used to identify a memory location. •

Variables • A variable is a string used to identify a memory location. • The amount of memory is determined by the type of data that it will store. • Typically, variable names need to be declared so the operating system can allocate sufficient space. • Then values of the specified type can be assigned, i. e. stored in that location.

Variable Names in VB • Must begin with a letter – Can include letters

Variable Names in VB • Must begin with a letter – Can include letters and numerals – Cannot include spaces • Use names that are descriptive • Capitalising convention – Interest. Rate, Initial. Capital

Variables • Local – Declared within a subprogram – Dim var. Name As data.

Variables • Local – Declared within a subprogram – Dim var. Name As data. Type • Global – Declared at the top of the code listing – Private var. Name As data. Type

Data Types Type Name Storage size Range of values Boolean 2 byte True or

Data Types Type Name Storage size Range of values Boolean 2 byte True or False (1 or 0) Byte 1 byte integers in the range 0 to 255 Char 2 bytes 0 to 65, 535 representing the Unicode character set Date 8 bytes time/date between 0: 00 on 1/1/0001 to 23: 59 on 12/31/9999 Double 8 bytes a real number; precision is about 14 digits to the right of the decimal point Integer 4 bytes integers in the range -2, 147, 483, 648 to 2, 147, 483, 647 Long 8 bytes very big! Short 2 bytes integers in the range -32, 768 to 32, 767 Single 4 bytes a real number, i. e. a number with a decimal (fractional) part; precision is limited to about 6 digits to the right of the decimal point. String depends on platform up to approximately 2 billion Unicode characters

The ASCII Character Set

The ASCII Character Set

Data Storage (Short type) 27 2 6 2 5 2 4 2 3 2

Data Storage (Short type) 27 2 6 2 5 2 4 2 3 2 2 128 64 32 16 8 4 1 1 1 128 +64 +32 +16 +8 +4 + =255 21 20 2 1 1 1 2 + 1

Data Storage (2 nd byte) 215 214 213 212 211 210 32768 16384 8192

Data Storage (2 nd byte) 215 214 213 212 211 210 32768 16384 8192 4096 2048 1024 1 1 1 32768+16384 +8192 +4096 +2048 +1024 29 512 1 +512 =65280 +255 65535 The largest Unsigned value that can be stored in 16 bits. How many patterns are there? 28 256 1 +256

Integer Storage • To store integers, half the combinations are used to represent negative

Integer Storage • To store integers, half the combinations are used to represent negative values. • The range for Integer type variables is: -32, 768 to +32767 • The MSB is used to represent the sign. • Which value of the sign bit (0 or 1) will represent a negative number?

Integer Storage (4 bytes) • High order bit (MSB) is worth 231 • The

Integer Storage (4 bytes) • High order bit (MSB) is worth 231 • The number of different combinations = 232 = 4, 294, 967, 296 • Half are used for negative values, so the range is – 2, 147, 483, 648 to + 2, 147, 483, 647

Long Integers • In 8 bytes there are 64 bits! • High order bit

Long Integers • In 8 bytes there are 64 bits! • High order bit (MSB) is worth 263. • The number of different combinations =264 =18, 446, 744, 073, 709, 650, 616

Data Type Conversion

Data Type Conversion