ec: An Engineering Calculator
This calculator is noteworthy in that it employs a stack model of computation (Reverse Polish Notation), it supports numbers with SI scale factors and units, and uses a text-only user interface.
Requires Python version 2.3 or later. Be aware that some features are not available with the earlier versions of Python.
More information on both ec and ec0 can be found at NurdleTech .
To get the source code:
$ git clone git://github.com/KenKundert/ec0.git
Once cloned, you can get the latest updates using:
$ git pull
Alternatively, you can download a zip file from:
If you go this route, you will have to unzip the file using the unzip command.
To run the regression tests:
This installs ec in
~/.local. Be sure to add
~/.local/bin to your
PATH. With early versions of python, you my see an ImportError when invoking
ec. If this is happens, you should add the site-packages directory onto your
python path using:
$ export PYTHONPATH=$HOME/.local/lib/python-<vers>/site-packages
if you use bash as your shell, or:
> setenv PYTHONPATH ~/.local/lib/python-<vers>/site-packages
if you use csh.
To read the EC manual:
$ man ec
On earlier versions of Linux you might need to supplement your man path using:
$ export MANPATH=$HOME/.local/man:$MANPATH
To run EC:
$ ec 0:
What follows is a brief tour of EC:
To perform operations in EC, you first enter the numbers, then the operators. In particular, as you enter the numbers they are pushed onto the stack. The operators then take numbers from the stack and replace them with the result. The operations are performed immediately and there is no use of parentheses to group calculations. Any intermediate results are stored on the stack until needed.
To add two numbers:
0: 4 5 + 9:
The prompt displays the value of the x-register.
You can string together an arbitrarily long calculation on a single line:
0: 4 5 + 6 7 + * 117:
Or, you can string a long calculation over multiple lines (this calculates the value of two parallel 100 ohm resistors):
0: 100 100: 100 100: || 50:
Select operators can be entered without preceding them with a space if they follow a number or a name. For example:
0: 4 5* 6 5+ * 220:
To store a value into a variable, type an equal sign followed by a name. To recall it, simply use the name:
0: 100MHz =freq 100MHz: 2pi* =omega 628.32M: 1pF =Cin 1pF: 1 omega/ Cin/ 1.5915K:
Display variables using:
628.32M: vars Cin = 1pF Rref = 50 Ohms freq = 100MHz omega = 628.32M 628.32M:
Rref is a special variable that is set by default to 50 Ohms, but you can change its value. It is used in dBm calculations.
EC supports units, but in a relatively conservative way. You can enter them and it remembers them, but they do not survive any operation other than a copy. In this way it should never display incorrect or misleading units, however it displays units when it can. For example:
0: 100MHz =freq 100 MHz: 2pi* "rads/s" =omega 628.32 Mrads/s: vars Rref = 50 Ohms freq = 100 MHz omega = 628.32 Mrads/s 628.32 Mrads/s: 2pi / 100M:
Notice that EC captured units on 100MHz and stored them into the memory freq. Also notice that the units of "rads/s" were explicitly specified, and they were also captured. Finally, notice that dividing by 2pi cleared the units.
Normally units are given after the number, however a dollar sign would be given immediately before:
0: $100M $100M:
You can enter hexadecimal, octal, or binary numbers, in either traditional programmers notation or in Verilog notation. For example:
0: 0xFF 255: 0o77 63: 0b1111 15: 'hFF 255: 'o77 63: 'b1111 15:
You can also display numbers in hexadecimal, octal, or binary in both
traditional or Verilog notation. To do so, use
0: 255 255: hex4 0x00ff: vbin 'b11111111:
You can convert voltages into dBm using:
0: 10 vdbm 30:
You can convert dBm into voltage using:
0: -10 dbmv 100 mV:
Both of these assume a load resistance that is contained in memory Rref, which by default is 50 Ohms.
At start up EC reads and executes commands from files. It first tries '~/.ecrc' and runs any commands it contains if it exists. It then tries './.ecrc' if it exists. Finally it runs any files given on the command line. It is common to put your generic preferences in '~/.exrc'. For example, if your are a physicist with a desire for high precision results, you might use:
eng6 h 2pi / 'J-s' =hbar
This tells EC to use 6 digits of resolution and predefines hbar as a constant. The local start up file ('./.ecrc') or the file given as a command line argument is generally used to give more project specific initializations. For example, in a directory where you are working on a PLL design you might have an './.ecrc' file with the following contents:
88.3uSiemens =kdet 9.1G 'Hz/V' =kvco 2 =m 8 =n 1.4pF =cs 59.7pF =cp 2.2kOhms =rz
EC also takes commands from the command line. For example:
$ ec -x "125mV 67uV / db" 65.417
-x tells ec to print out the value of the x register when it
terminates. Without it you would not see the result.
EC prints back-quoted strings while interpolating the values of registers and variables when requested. For example:
$ ec 'degs 500 1000 rtop "V/V" `Gain = $0 @ $1.`' Gain = 1.118 KV/V @ 26.565 degs.
You can get a list of the actions available with:
You can get help on a specific topic, such as //, with:
You can get a list of the help topics available with:
There is much more available that what is described here. For more information, run:
$ man ec
You can quit the program using:
(or :q or ^C).