Editing Vilnius BASIC (section)

===Numeric variables, operators and functions===
As with most dialects, variable names had to start with a letter and could be followed by more letters or digits. Variable names could be any length, but only the first two characters were stored or matched, meaning that typing {{code|PRT001{{=}}1}} followed {{code|PR{{=}}5}} would result in a single variable in memory known as PR with the value 5.

Vilnius BASIC had four basic data types, strings, single and double-precision [[floating point]] numbers, and integers. Unless otherwise denoted, variables were assumed to be double-precision, stored in eight bytes and providing about 17 digits of precision. For comparison, most MS dialects used a [[Microsoft Binary Format|5-byte format]] for floating point. If {{code|!}} was suffixed to the variable name, the value was stored in single-precision using four bytes with about 7 digits of precision.  {{code|%}} specified an integer, using a single 16-bit word to store values between -32768 and +32767. If a value with more precision was assigned to a variable with less, any excess was simply discarded; {{code|A%{{=}}1.5}} will result in A% having the value 1.

Numeric constants in the [[source code]] could also be specified as a particular type using the same indicators; {{code|50%}} would store the constant as an integer, {{code|0.05!}} or {{code|5E-02}} stores a single-precision value 0.05, and {{code|0.05}} or {{code|5D-02}} stores the same value in the default double-precision format. Vilnius also had the additional ability to allow numeric constants to be typed in as strings of binary, [[octal]] or [[hexadecimal]] characters, by prefixing the string with {{mono|&}} and a single letter indicating the type, B, O, H. For instance, {{code|A{{=}}&H9A8B}} would convert the hexadecimal string H9A8B to the equivalent decimal value 39563 and store that in A.

Operators for numerical values included {{code|+, -, *, /, ^}} adding {{code|\}} for integer division and {{code|MOD}} for the remainder. Thus {{code|5\2}} returns 2, while {{code|5 MOD 2}} returns 1. Numeric functions include the standard {{code|ABS, ATN, COS, EXP, INT, LOG, RND, SGN, SIN, SQR, TAN}}. It also included the {{code|FIX}} operator, which is similar to {{code|INT}} but always truncates toward zero so that {{code|FIX(-1.5)}} returns -1 instead of -2 like INT.

In addition to [[PEEK and POKE]], which returned 16-bit values, the system also offered {{code|OUT and INP}}, which were similar but applied a [[bit mask]] to the values to allow individual bits to be set or cleared.{{sfn|Manual|p=46}} {{code|CLS}} cleared the screen. System functions include {{code|FRE}} which returned the amount of free memory, and {{code|TAB}} which moved to the given column. {{code|AT (x,y)}} worked in a similar fashion to TAB, but moved the cursor to the given X,Y location.