Programs manipulate data. The data can be numeric or textual, but the data must be presented according to the rules of the Sheerpower language.

Sheerpower accepts three basic types of data:

1. integer numbers
2. real numbers
3. string (textual) data

The following sections describe each of the three types of data.

An integer number is a whole number with no fractional part. The following are examples of integers:

+5% 894% -369004%

Integers can be positive or negative. Integer constants can end with a trailing percent sign (%). About integers:

• Names for integer variables, arrays or functions must be designated by a trailing percent sign (%) or declared with a DECLARE statement.
• A negative integer constant is designated by a leading minus sign.
• A positive integer constant can be designated by a leading plus sign or by the absence of a sign.
• Integers have a size of 32 bits.
• Sheerpower allows integer numbers anywhere in the range of -2147483648 to +2147483647.

A real number can have a fractional part. The following are real constants:

5.4 894.0 -369004

Real numbers can be positive or negative. Any number that is not designated as an integer or a string is treated as a real number.

A real number without a decimal point is called an ambiguous constant. About real numbers:

• A variable, array or function whose name has no trailing % or $ is treated as a real number unless it is declared.
• A negative real constant has a leading minus sign.
• A positive real constant can have a leading plus sign or no sign.
• Ambiguous constants are treated as real numbers with a fractional part of 0 (5 = 5.0).
• Real numbers can have 18 digits to the LEFT of the decimal point, and 16 digits to the right. The largest number is: 999999999999999999.9999999999999999
• Sheerpower REAL NUMBERS use a patented "exact math" internal representation that avoids the "penny rounding" problems found in traditional programming languages.

Here is an example of Sheerpower exact math:

Example 4-1 Sheerpower Exact Math

x = 0 for i = 1 to 10000 x = x + .01 next i if x = 100.00 then print 'It is right.' It is right.

If you try this example in another programming language (Visual Basic or C++ for example), you will not get the correct answer. Here is another example:

Example 4-2 Sheerpower Exact Math

print 123456789.012345 * 87654321.123456789 10821521028958940.344459595060205

4.1.3 String Data

String data consists of text. Text can consist of any characters. All of the following are valid string constants:

Example 4-3 String data

'Hello, Fred.' 'Account number (##-####)' '65'

About string data:

• String constants must be enclosed in single or double matching quotes. String variables must be designated by a trailing dollar sign ($) or declared with a DECLARE statement.
• The maximum size of a Sheerpower string is 64 MB, or 67,108,864 bytes.
• String variables are dynamic in length.

Boolean variables represent either a TRUE or FALSE condition. These variables can be expressed with a trailing "?". For example:

Example 4-4 BOOLEAN Variables

done? = FALSE do input 'Ready': ans$ if _exit then done? = true if _back then done? = true loop until done? end Ready? exit

4.3 Expressions

Expressions can be:

• constants
• simple variables
• array elements, which are a type of variable
• table or structure references, which are a feature of the Sheerpower data table/structure system
• substrings
• compound expressions, which are any combination of the above operands separated by operators

A constant is a value that does not change during a program execution. Constants can be any of the three data types: integer numeric, real numeric or string.

Integer numeric constants are written with digits, with no decimal fraction. An integer constant can end with a percent sign. Examples:

235 412%

Real numeric constants are written with a sign, digits, and a decimal point. For example, 5.38 is a real numeric constant.

String constants must be enclosed in quotes. The quotes are called string delimiters. They tell Sheerpower where the string begins and ends. The quotes are not considered part of the string. Everything within the quotes is considered part of the string. Note that the following strings are different:

Example 4-5 String Constants and Delimiters

print 'Account number (##-####)' print ' Account number (##-####)' end Account number (##-####) Account number (##-####)

An empty string is called a null string. A null string is indicated by a pair of quotes with nothing between them ("").

String delimiters can be single quotes (') or double quotes ("). However, the quotes must match and be paired.

Quotes can be included as part of a string by using them within the string delimiters. For example:

"Message'Time to go home!'"

The string part of this is:

Message 'Time to go home!'

The delimiter quotes can be used within a string by repeating them twice. For instance:

"Message ""Time to go home!"""

The string part of this is:

Message "Time to go home!"

Variables are a way of storing values that can change in the program during execution. A variable names a storage location. The value of the variable is stored in this location. Here are two types of variables:

• simple variables such as: AVERAGE and NAME$
• array elements such as: AVERAGE(3) and NAME$(2,12)

Two other constructs are used in ways similar to variables---you can use them in expressions and assign values to them:

• substrings such as: NAME$[7:12]
• structure references such as: SALES(AVERAGE) and CLIENT(PHONE)

Variables are represented by a name consisting of a letter or series of letters, numbers and underscore characters. Variables:

• must start with a letter
• can be followed by a proper data type designation (% for integers, $ for strings and ? for BOOLEANS)
• can be declared explicitly

Some examples of valid variables are:

TODAY$ X% Z INDEX

• Variables can be integer numeric, real numeric or string.
• Integer variables can contain only integer values.
• If a real numeric value is assigned to an integer variable, Sheerpower rounds the real number and uses the resulting integer.
• String variable names can have a trailing dollar sign ($).
• If numeric data is assigned to a string variable, an exception occurs.

The following are examples of string variables:

TODAY$ X$ LAST_NAME$ ANSWER$

• A variable that is not followed by a $, % or ? is treated as a real numeric variable unless it is declared.
• If string data is assigned to a real numeric variable, an error will result.
• If integer data is assigned to a real numeric variable, Sheerpower treats it as a real number with a fractional part of 0.

The following are examples of real numeric variables:

INDEX Z COUNTER AMOUNT

Sheerpower uses the last assigned value when a variable is referenced. See Section 5.7, Private Variables in Routines for more information on using variables.

An array is a variable that consists of a group of elements. Each element represents a storage location. A different value can be assigned to each element. Here is an example of an array:

QUANTITY(1) QUANTITY(2) QUANTITY(3) QUANTITY(4) QUANTITY(5)

To indicate which element to access, use numbers after the array name, called subscripts. The subscripts are enclosed in parentheses. Example: amount(3,2)

Subscripts must be given as integers. If a real numeric subscript is given, it will be rounded and the integer portion used. Arrays can contain real numeric, integer or string values. String and integer arrays are designated by placing the appropriate symbols after the array name and before the subscript. For example:

a$(5,10) a%(5,10)

About arrays:

• Arrays must be defined with the DIM statement and can be redefined with the REDIM statement.
• Arrays can have up to 32 dimensions.
• An array can have as many elements as memory allows.
• Integer and string arrays must be designated by the appropriate symbol (% for integers, $ for strings) or else they must be declared.
• Subscripts must be integers. Real subscripts are rounded.
• Multiple subscripts must be separated by commas.
• The default low bound for an array is 1 or the number indicated with the OPTION BASE statement (See Section 5.8.4).
• You can indicate the low bound explicitly with a TO clause:
  DIM COSTS(5 TO 10).