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Command Reference
github-actions[bot] edited this page Apr 3, 2026
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← Graphics and Multimedia | Next: IDE
These commands are available in the interactive REPL. They control the interpreter itself — loading, saving, debugging, and inspecting programs — and are not valid inside a running BASIC program.
| Command | Description | Syntax |
|---|---|---|
Run |
Execute the program in memory | Run [linenumber] |
Cont |
Continue after a Stop or breakpoint |
Cont |
Resume |
Resume from the next line after interrupt | Resume |
Break |
Set a breakpoint, optionally conditional | Break [[linenum] [If expr]] |
RmBrk |
Remove a breakpoint | RmBrk linenum |
ClrBrk |
Remove all breakpoints | ClrBrk |
Load |
Load a program file into memory | Load filename |
Save |
Save the current program to a file | Save filename |
Exec |
Load and run a program file | Exec filename |
List |
List all or part of the program | List [from[-to]] |
New |
Clear program and all variables | New |
Clr |
Clear all variables (keep program) | Clr |
Renum |
Renumber program lines | Renum [increment] |
Grep |
List lines matching a pattern | Grep pattern |
Vars |
Show current run-time variables | Vars |
Meta |
Show build metadata | Meta |
Ver |
Print interpreter version | Ver |
TrOn |
Enable program tracing | TrOn |
TrOff |
Disable program tracing | TrOff |
StOn |
Enable step-by-step execution | StOn |
StOff |
Disable step-by-step execution | StOff |
Pwd |
Print current working directory | Pwd |
Cd |
Change working directory | Cd path |
Help |
Show help for a keyword | Help [keyword] |
Apropos |
Search help descriptions | Apropos keyword |
! |
Execute a shell command | ! shell_command |
Exit |
Quit the interpreter | Exit |
| Instruction | Syntax | Description |
|---|---|---|
Dim |
Dim var[(n)] [As Type] |
Declare variable or array |
ReDim |
ReDim var(n) |
Resize array (clears content) |
Const |
Const name [As Type] = value |
Declare a constant |
Let |
[Let] var = expr |
Assign a value (keyword optional) |
Sub |
Sub name([ByRef|ByVal] params) … End Sub
|
Define a subroutine |
Function |
Function name([ByRef|ByVal] params) [As Type] … End Function
|
Define a function |
Call |
Call name(args) |
Invoke a Sub or Function (optional keyword) |
ByRef |
ByRef param As Type |
Pass parameter by reference (mutations propagate back) |
ByVal |
ByVal param As Type |
Pass parameter by value (default) |
Struct |
Struct name … End Struct
|
Define a composite type |
Include |
Include "file.bas" |
Load and execute another source file |
End |
End |
Stop program execution |
Stop |
Stop |
Break into REPL (resume with Cont) |
| Instruction | Syntax | Description |
|---|---|---|
If |
If expr Then … [ElIf expr Then …] [Else …] End If |
Conditional branch |
For |
For var=x To y [Step z] … Next [var]
|
Counted loop |
While |
While cond … Wend | End While
|
Pre-condition loop |
Do |
Do … Loop While cond
|
Post-condition loop |
Exit For |
Exit For |
Break out of For loop |
Exit While |
Exit While |
Break out of While loop |
Exit Do |
Exit Do |
Break out of Do loop |
Exit Sub |
Exit Sub |
Return from Sub early |
Exit Function |
Exit Function |
Return from Function early |
GoTo |
GoTo label | linenum |
Unconditional jump |
GoSub |
GoSub label | linenum |
Call a subroutine |
Return |
Return |
Return from GoSub |
On |
On expr GoTo label1[, label2, …] |
Computed branch |
| Instruction | Syntax | Description |
|---|---|---|
Print |
Print [expr[; | , …]] |
Output to console |
Write |
Write [expr[; | , …]] |
Output without trailing newline |
Print# |
Print# filenum, expr |
Output to file |
Input |
Input [prompt;] var |
Read from console |
Input# |
Input# filenum, var |
Read from file |
Read# |
Read# filenum, var, size |
Raw binary read |
Open |
Open filename For mode As #n |
Open a file |
FOpen |
FOpen filename, mode$, n |
Open a file (C-style mode string) |
Close |
Close #n |
Close a file |
Seek |
Seek filenum, pos, origin |
Move file pointer |
Flush |
Flush filenum |
Flush file buffer to disk |
Locate |
Locate row, col |
Move text cursor (1-based) |
Cls |
Cls |
Clear the console screen |
Beep |
Beep |
Sound the system beep |
| Instruction | Syntax | Description |
|---|---|---|
Delay / Sleep
|
Delay seconds |
Pause execution (in seconds) |
MDelay |
MDelay milliseconds |
Pause execution (in milliseconds) |
| Instruction | Syntax | Description |
|---|---|---|
Data |
Data expr1[, expr2, …] |
Store constant data values |
Read |
Read var1[, var2, …] |
Read from the Data store |
Restore |
Restore [index] |
Rewind or reposition Data pointer |
| Instruction | Syntax | Description |
|---|---|---|
Line |
Line x1,y1,x2,y2,color |
Draw a line |
Rect |
Rect x1,y1,x2,y2,color |
Draw rectangle outline |
FillRect |
FillRect x1,y1,x2,y2,color |
Draw filled rectangle |
Ellipse |
Ellipse x1,y1,x2,y2,color |
Draw ellipse outline |
FillEllipse |
FillEllipse x1,y1,x2,y2,color |
Draw filled ellipse |
SetPixel |
SetPixel x,y,color |
Draw a single pixel |
TextOut |
TextOut x,y,text$,color |
Draw text at pixel coordinates |
PlotImage |
PlotImage bitmap$,x,y |
Draw a BMP image |
ScreenLock |
ScreenLock |
Suspend screen refresh (begin compositing frame) |
ScreenUnlock |
ScreenUnlock |
Present back buffer to screen (end frame) |
Refresh |
Refresh |
Force immediate blit (lock state unchanged) |
| Instruction | Syntax | Description |
|---|---|---|
ChDir |
ChDir path$ |
Change working directory |
Shell |
Shell "command" |
Execute a shell command |
Randomize |
Randomize |
Seed the random number generator with current time |
| Function | Returns | Description |
|---|---|---|
Abs(x) |
Double | Absolute value |
Int(x) |
Integer | Truncate toward zero |
TruncF(x) |
Double | Round toward zero (double result) |
Sign(x) |
Integer | −1, 0, or 1 |
Sqr(x) / Sqrt(x)
|
Double | Square root |
Pow(x,y) |
Double | x raised to the power y |
Exp(x) |
Double | e^x |
Log(x) |
Double | Natural logarithm |
Log10(x) |
Double | Base-10 logarithm |
Sin(x) |
Double | Sine (x in radians) |
Cos(x) |
Double | Cosine (x in radians) |
Tan(x) |
Double | Tangent (x in radians) |
ASin(x) |
Double | Arc sine (result in radians) |
ACos(x) |
Double | Arc cosine (result in radians) |
ATan(x) |
Double | Arc tangent (result in radians) |
Sinh(x) |
Double | Hyperbolic sine |
Cosh(x) |
Double | Hyperbolic cosine |
Tanh(x) |
Double | Hyperbolic tangent |
PI() |
Double | π ≈ 3.14159265358979 |
Rnd(x) |
Double | Random number in [0,1); x<0 reseeds the generator |
Min(x,y) |
Double | Smaller of x and y |
Max(x,y) |
Double | Larger of x and y |
Conv(v1,v2[,c1,c2]) |
Array | Discrete convolution of two numeric vectors |
| Function | Returns | Description |
|---|---|---|
Len(s$) |
Integer | Length in characters |
Left$(s$,n) |
String | First n characters |
Right$(s$,n) |
String | Last n characters |
Mid$(s$,n,m) |
String | m characters from 1-based position n |
SubStr$(s$,n,m) |
String | m characters from 0-based offset n |
PStr$(s$,pos,c$) |
String | Return s$ with character at 0-based pos replaced by c$ |
InStr(s$,t$) |
Integer | 1-based position of t$ in s$; −1 if absent (case-insensitive) |
InStrCS(s$,t$) |
Integer | Same but case-sensitive |
UCase$(s$) |
String | Convert to upper case |
LCase$(s$) |
String | Convert to lower case |
Str$(x) |
String | Number to string |
StrP$(x,p%) |
String | Number to string with p% significant digits |
Hex$(x) |
String | Hexadecimal representation |
Val(s$) |
Double | Parse string as floating-point number |
Val%(s$) |
Integer | Parse string as integer |
Asc(s$) |
Integer | Unicode code point of first character |
Chr$(n) |
String | Character from Unicode code point |
Spc(n) |
String | String of n spaces |
Eval(s$) |
Any | Evaluate a nuBASIC expression string at run time |
| Function | Returns | Description |
|---|---|---|
InKey$() |
String | Non-blocking key read; empty string if no key is waiting |
Input$(n) |
String | Block until exactly n characters are read |
GetVKey() |
Integer | Read next virtual key code from input |
| Function | Returns | Description |
|---|---|---|
EOF(n) |
Integer | 1 if at end-of-file; 0 otherwise |
FError(n) |
Integer | Non-zero if an error has occurred on file n |
FTell(n) |
Integer | Current byte offset in file n |
FSize(n) |
Integer | Total size in bytes of file n |
Errno() |
Integer | System error code from the last failed operation |
Errno$(n) |
String | Human-readable description for error code n |
MkDir(path$) |
Integer | Create a directory; returns 0 on success |
RmDir(path$) |
Integer | Remove a directory; returns 0 on success |
Erase(path$) |
Integer | Delete a file; returns 0 on success |
Pwd$() |
String | Current working directory |
GetEnv$(var$) |
String | Value of an environment variable |
SetEnv(var$,val$) |
Integer | Set an environment variable |
UnsetEnv(var$) |
Integer | Unset an environment variable |
| Function | Returns | Description |
|---|---|---|
SysTime$() |
String | Current local time and date as a string |
Time() |
Integer | Seconds elapsed since the Unix Epoch |
SysHour() |
Integer | Current hour (0–23) |
SysMin() |
Integer | Current minute (0–59) |
SysSec() |
Integer | Current second (0–59) |
SysDay() |
Integer | Day of the month (1–31) |
SysMonth() |
Integer | Month (0–11; January = 0) |
SysYear() |
Integer | Full year (e.g. 2026) |
SysWDay() |
Integer | Day of week (0=Sunday … 6=Saturday) |
SysYDay() |
Integer | Day of year (1–365) |
GetPlatId() |
Integer | 1 = Windows, 2 = Linux/other |
GetAppPath$() |
String | Full path of the nuBASIC executable |
Ver$() |
String | nuBASIC version string |
| Function | Returns | Description |
|---|---|---|
Rgb(r,g,b) |
Integer | Compose an RGB color from 0–255 components |
GetPixel(x,y) |
Integer | Read the color of a pixel |
GetMouseX() |
Integer | Mouse cursor X in pixels |
GetMouseY() |
Integer | Mouse cursor Y in pixels |
GetMouseBtn() |
Integer | Mouse button bitmask (1=left, 2=middle, 4=right) |
GetSWidth() |
Integer | Width of the drawable client area in pixels |
GetSHeight() |
Integer | Height of the drawable client area in pixels |
GetWindowX() |
Integer | Window left edge position on screen |
GetWindowY() |
Integer | Window top edge position on screen |
GetWindowDx() |
Integer | Total window width in pixels |
GetWindowDy() |
Integer | Total window height in pixels |
MoveWindow(x,y,w,h) |
Integer | Move and resize the working window |
SetTopMost() |
Integer | Make the window always-on-top |
MsgBox(title$,msg$) |
Integer | Show a modal dialog; returns > 0 if confirmed |
PlaySound(file$,async%) |
Integer | Play a WAV file (async%=1 returns immediately) |
| Function | Returns | Description |
|---|---|---|
HSet(hash$,key$,val) |
— | Insert or update an entry |
HGet(hash$,key$) |
Any | Retrieve the value for a key |
HChk(hash$,key$) |
Boolean | True if the key exists in the table |
HCnt(hash$) |
Integer | Number of entries in the table |
HDel(hash$[,key$]) |
— | Delete a single key, or the whole table if key omitted |
| Function | Returns | Description |
|---|---|---|
Not(x) |
Integer | Logical NOT: 1 if x=0, 0 otherwise |
bNot(x) |
Integer | Bitwise NOT of x |
SizeOf(x) |
Integer | Size in bytes of a variable or entire array |
SizeOf@(x) |
Integer | Number of elements in an array |
| Operator | Description | Example |
|---|---|---|
+ |
Add numbers or concatenate strings |
a + b, "Hi" + name$
|
- |
Subtract; unary negation |
a - b, -x
|
* |
Multiply | a * b |
/ |
Divide (floating-point result) | a / b |
\ or Div
|
Integer divide (truncates) | a \ b |
Mod |
Modulo — remainder after integer division | a Mod b |
^ |
Exponentiation | 2 ^ 10 |
++ |
Increment prefix | ++i% |
-- |
Decrement prefix | --i% |
= |
Equal (comparison) or assignment | a = b |
<> |
Not equal | a <> b |
< > <= >=
|
Ordered comparison | a < b |
And |
Logical AND | a And b |
Or |
Logical OR | a Or b |
Xor |
Logical exclusive OR | a Xor b |
Not |
Logical NOT | Not(x) |
bAnd |
Bitwise AND | a bAnd b |
bOr |
Bitwise OR | a bOr b |
bXor |
Bitwise XOR | a bXor b |
bNot |
Bitwise NOT | bNot(x) |
bShl |
Shift left | a bShl 2 |
bShr |
Shift right | a bShr 2 |
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