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QCalc Programmer's Calculator

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QCalc is a powerful, cross-platform calculator specifically designed for embedded systems programmers. The calculator accepts whole expressions in the C-syntax and displays results simultaneously in decimal, hexadecimal, and binary without the need to explicitly convert the result to these bases.

QCalc user interface
The calculator is a console application, where you can type complete C expressions. You can also copy-and-paste expressions into and from the calculator console to use them almost directly in your C code.

QCalc Usage

QCalc is included in the QTools Collection in the sub-directory qtools/qcalc/ and consists of a single file qcalc.py. To launch QCalc, you need to open this file with python.

You use QCalc by typing (or pasting) an expression at the > prompt and pressing Enter to evaluate the expression. You can conveniently edit any expression already inside the user input field, and you can recall the previous expressions by means of the Up and Down keys.

You quit the calculator by Enter without entering an expression.

Batch Mode

If you provide the optional [expression] argument, QCalc will evaluate the expression, print the result and terminate. For example:

qcalc "2*3 + (1 << 3)"
QCalc Programmer's Calculator 6.9.4 running on Python 3.9.1
(c) 2005-2021 Quantum Leaps, www.state-machine.com

2*3 + (1 << 3)
= 14 | 0x0000'000E | 0b00000000'00000000'00000000'00001110

Interactive Mode

Otherwise, if no [expression] argument is provided, QCalc will start in the interactive mode, where you can enter expressions via your keyboard.

QCalc on Windows

The python interpreter is included in the QTools collection for Windows. The QTOOLS%\bin directory also contains the qcalc.bat batch file and a shortcut qcalc, which you can copy to your desktop:

Shortcut for launching QCalc

QCalc Features

Expressions in C-Syntax

The most important feature of QCalc is that it accepts expressions in the C-syntax—with the same operands and precedence rules as in the C or C++ source code. Among others, the expressions can contain all bit-wise operators (<<, >>, |, &, ^, ~) as well as mixed decimal, hexadecimal and even binary constants. QCalc is also a powerful floating-point scientific calculator and supports all mathematical functions (sin(), cos(), tan(), exp(), ln(), ...). Some examples of acceptable expressions are:

((0xBEEF << 16) | 1280) & ~0xFF—binary operators, mixed hex and decimal numbers
($1011 << 24) | (1280 >> 8) ^ 0xFFF0—mixed binary, dec and hex numbers
(1234 % 55) + 4321//33—remainder, integer division (note the // integer division operator
pow(sin(and),2) + pow(cos(and),2)—scientific floating-point calculations, and-variable

QCalc internally uses the Python command eval to evaluate the expressions. Please refer to the documentation of Python math expressions for more details of supported syntax and features.

Automatic Conversion to Hexadecimal and Binary

If the result of expression evaluation is integer (as opposed to floating point), QCalc automatically displays the result in hexadecimal and binary formats (see QCalc screenshot). For better readability, the hex display shows an apostrophe between the two 16-bit half-words (e.g., 0xDEAD'BEEF). Similarly, the binary output shows an apostrophe between the four 8-bit bytes (e.g., 0b11011110'10101101'10111110'11101111).

Hexadecimal and Binary Numbers

As an extension to the C-syntax, QCalc supports both hexadecimal numbers and binary numbers. These numbers are represented as 0x... and0b..., respectively, and can be mixed into expressions. Here are a few examples of such expressions:

(0b0110011 << 14) & 0xDEADBEEF
(0b0010 | 0b10000) * 123

History of Inputs

As a console application QCalc "remembers" the history of the recently entered expressions. You can recall and navigate the history of previously entered expressions by pressing the Up / Down keys.

The and Variable

QCalc stores the result of the last computation in the and variable. Here are some examples of expressions with the and variable:

1/and—find the inverse of the last computation
log(and)/log(2)—find log-base-2 of the last computation

64-bit Range

QCalc supports the 64-bit range and switches to 64-bit arithmetic automatically when an integer result of a computation exceeds the 32-bit range. Here are some examples of the 64-bit output:

> 0xDEADBEEF << 27
= 501427843159293952 | 0x06F5'6DF7'7800'0000
= 0b00000110'11110101'01101101'11110111'01111000'00000000'00000000'00000000
> 0xDEADBEEF << 24
= 62678480394911744 | 0x00DE'ADBE'EF00'0000
= 0b00000000'11011110'10101101'10111110'11101111'00000000'00000000'00000000
> 0xDEADBEEF << 34
! out of range

Error handling

Expressions that you enter into QCalc might have all kinds of errors: syntax errors, computation errors (e.g., division by zero), etc. In each of these cases, QCalc responds with the Error message and an explanation of the error:

> (2*4) + )
Traceback (most recent call last):
  File "C:\qp\qtools\qcalc\qcalc.py", line 54, in _main
    result = eval(expr)
  File "<string>", line 1
    (2*4) + )
SyntaxError: unmatched ')'

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