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Learn about operators like exponentiation, multiplication, and division in VB, along with data types, variables, and storage concepts. Understand integer and real division, addition, subtraction, and how to evaluate expressions efficiently. Dive into variable naming conventions and data type conversion.
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Operators & Identifiers The Data Elements
exponentiation multiplication division (real) division (integer quotient) division (integer remainder) addition Subtraction assignment ^ * / \ Mod + - = Arithmetic Operators
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 and numerals • Cannot include spaces • Use names that are descriptive • Capitalising convention • InterestRate, InitialCapital
Variables • Local • Declared within a subprogram • Dim varName As dataType • Global • Declared at the top of the code listing • Private varName As dataType
Data Storage (Short type) 27 26 25 24 23 22 21 20 128 64 32 16 8 4 2 1 1 1 1 1 1 1 1 1 128 +64 +32 +16 +8 +4 + 2 + 1 =255
Data Storage (2nd byte) 215 214 213 212 211 210 29 28 32768 16384 8192 4096 2048 1024 512 256 1 1 1 1 1 1 1 1 32768+16384 +8192 +4096 +2048 +1024 +512 +256 =65280 +255 65535 The largest Unsigned value that can be stored in 16 bits. How many patterns are there?
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 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 (MSB) is worth 263. • The number of different combinations • 264 • 18,446,744,073,709,650,616