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Assam-Calcu: A Programmable All-Purpose Calculator

Assam-Calcu is a 12-digit multi-purpose calculator that can store and recall millions of your old calculations - whether ordinary or scientific. It may also be easily programmed to run hundreds of calculation-steps in one go. It is designed to be equally convenient for purposes as varied as the simplest grocery arithmetic as well as the most advanced technological computations.
The basic operation in Assam-Calcu is execution of a simple command-line (say, 'Answer = 673+245'), of which the left side is a variable (say, 'Answer'), and on the right side of which lies an expression (say '55*4' or 'Mass*(3.0E8)**2'). If the right side uses one or more variable(s), e.g., 'Mass', their values must have been defined in earlier steps. Compared to most calculator-instruments, Assam-Calcu offers the much wider range of 9.9E+300 to 1.0E-300 for its results. It also contains a database of values for popular constants & conversion-factors. Versions 3.x allow definition of several pre-defined SI-unit constants in one go.

This Windows software (screenshot shown below) has been developed by Rituraj Kalita, a resident of Guwahati, Assam (India) first during December, 2006 (using the Visual FoxPro 6 platform), and is being distributed as a freeware (i.e., free software) by Eastern Star Software, Guwahati.

Fig.: Assam-Calcu Screenshot

Now, please do spare a few more minutes to go through the following 'Tutorials' and 'Frequently Asked Questions'!

A. Tutorials:

1. Personal Grocery Calculations in an Indian Town:
Suppose someone in a small town in India has just bought from the local grocer's some 5 kg of rice at Rs. (i.e., Indian Rupees) 15 per kg, 2 kg of potato at Rs. 8 per kg, 1.5 kg of lentil (masur dal) at Rs. 28 per kg, and half a kg of onion at Rs. 15 per kg. To calculate this, proceed as follows: double-click at the Assam-Calcu desktop-icon to run, then click at the Reset Above Command button just ONCE to clear the right side of the command, then type (on that right side) 5*15 + 2*8 + 1.5*28 + 0.5*15 (so as to represent above calculation; you may also add there a subsequent comment, say: && rice, potato, lentil, onion respectively. Press Ctrl+End (or press Alt+R or click at the Run Above Command or Calculate it! button) to run this command. The result (140.5) will be displayed, and the command with the result will remain stored forever (may be recalled anytime later with just a button-click at the Get Old Comm button)!

2. Calculating the Equated Monthly Installment (EMI) for an Indian bank loan:
The loans that the nationalized banks in India provide to individuals for buying a car or building a house etc. are generally to be repaid in equated monthly installments (EMIs). To calculate the EMI, we first need to find what the loan amount (AmLoan) would have become during the loan period, in absence of any payment. This is, clearly,
FinAmt = AmLoan*(Factor**NYears), where Factor = 1 + PCRate/100, PCRate (say, 12) being the percentage yearly rate of interest and NYears (say, 2.5) is the loan period in years. Using the value for FinAmt, the EMI may be finally calculated by the relation (explanation omitted here):
EMI = Round(FinAmt*(Factor**(1/12) - 1)/(Factor**NYears - 1),0) where Round(x,0) function rounds off the expression x to the nearest integer. Let us here think of a loan amount of Rs. 60,000 to be paid in a period of 30 months (i.e., via 30 EMIs), where the rate of interest is 12% per annum. Opening Assam-Calcu, we, so, run the commands
AmLoan = 60000, NYears = 2.5 and PCRate = 12. Then we calculate Factor = 1 + PCRate/100 and then
FinAmt = AmLoan*(Factor**NYears). Then finally we calculate
EMI = Round(FinAmt*(Factor**(1/12) - 1)/(Factor**NYears - 1),0), thereby arriving at the value 2308 (i.e., Rs. 2,308) for the EMI. Note: This calculation gives us only an approximate value for the EMI. The exact bank rule for the calculation may somewhat differ, leading to some variations for the EMI (an actual EMI at the State Bank of India, for the aforesaid situation, was Rs. 2,347).

3. Calculation of the Translational Partition Function of a Given Volume of a Particular Gas Kept at a Given Temperature:
In chemistry, one needs to calculate the translational partition function (q_tr) of a gas-system using relation: q_tr = (((2*pai*m0*k*T)**1.5)/(h**3))*V, where pai is 3.1416, m0 is the mass of a gas molecule equaling Mm/Na (where Mm is the molar mass and Na is the Avogadro number), k is the Boltzmann constant, T is the Kelvin-scale temperature, h is the Planck constant and V is the volume of the system. For oxygen gas (molar mass 0.032 kg/mol) enclosed in a container of volume 0.005 cubic meter at 27 Centigrade temperature (i.e., at 300.15 Kelvin), we may proceed as (knowing that Na is 6.022E+23, k is 1.381E-23 J/(K-mol) and that h is 6.626E-34 J-s): (i) Click twice at 'Reset Above Command' button to clear the old command (ii) Enter & Run the following commands one by one: pai = 3.1416, Mm = 0.032, Na = 6.022E+23, m0 = Mm/Na, k = 1.381E-23, T = 300.15, h = 6.626E-34, V = 0.005 and then finally q_tr = (((2*pai*m0*k*T)**1.5)/(h**3))*V (iii) In that final step you've got the result 8.84909618558E+029, haven't you?
Note: (i) Most of the scientific calculators (i.e., the instrument, not a software) won't be able to directly find h**3, as it is (in the popular SI unit) less than 1.0E-100. (ii) Performing this multi-step calculation in such a simple non-programmable calculator instrument is as such quite a cumbersome job (even if there arises no problem about the h**3 calculation)! (iii) To get the above steps in the form of a (FoxPro/ Visual-FoxPro) program-listing, re-run the above command steps again using an Assam-Calcu Re-Run command, as explained in the 5th tutorial below. (iv) The values of the above constants p, k, R, NA, T, h etc. (in SI unit) may also be easily brought onto the command-line by clicking at the Constants button, and then by clicking at the entry for the desired (pre-defined) constant. This inbuilt list of constants & conversion factors has been carefully collated (for the physical-science constants are used the 2006 CODATA recommended values) with help from some standard resources, as detailed here. (v) To find q_tr for nitrogen gas (Mm = 0.028) enclosed in 0.01 cubic meter volume at 325 K temperature, may now just run (one by one) Mm = 0.028, m0 = Mm/Na, T = 325, V = 0.01 and then q_tr = (((2*pai*m0*k*T)**1.5)/(h**3))*V (the value thus obtained is 1.63214414284E+30, isn't it?)

4. Exact Calculation of the Constant in the Wien's Displacement Law (in Physics) about Blackbody Radiation (Using an Iterative Method):
While deriving the Wien's displacement law (regarding the wavelength for the most intense radiation) from the Planck's law about blackbody radiation, it is found that the Wien's constant b equals (hc/yk), where h is the Planck constant, c is the speed of light in vacuum, k is the Boltzmann constant, and y is the numerical solution of the transcendental equation y*exp(y)/(exp(y)-1) = 5, or in other words, of the equation y = 5 - 5*exp(-y). The iterative method for solution of this equation (in the last form) has a fast convergence, and so starting with an approximate value of y (say, 5) we may continue iterations using this relation y = 5 - 5*exp(-y). But at first, immediately after opening Assam-Calcu, let us just click at the Define Listed SI-Unit Constants button (or press Alt+D) to automatically define the SI-unit values for a set of common constants including h, c and k. Now to perform the iteration steps, we start by running the command y = 5 and then the command y = 5 - 5*exp(-y). After this, we need to just press Ctrl+End again and again to run this same command repeatedly. We see that just with 8 steps, the value of y accurately converges to 4.96511423174, thus giving the value of the constant b [employing an appropriate Assam-Calcu command b = h*c/(y*k)] as 0.00289776536 m K.
Note: Similarly, you may easily solve the equation y = cos(y), starting with y = 0, reaching the solution y = 0.73908513322 in 74 steps -- yet within a duration of at most two minutes.

5. Using Gauss-Seidel Iteration Method for Solution of a System of Linear Equations in Several Unknowns, via Assam-Calcu 'Re-Run' Command:
Let us now solve the set of three linear equations (x -2*y + 3*z = 10, x - 3*y + 2*z = 1, 3*x + y - z = 8) in the three unknowns (x, y, z) by using the Gauss-Seidel iterative method. As per the well-known process of judging the absolute values of the coefficients, we re-arrange the above set as: (3*x + y - z = 8, x - 3*y + 2*z = 1, x - 2*y + 3*z = 10) and then proceed to iterate using the following (equivalent) relations: x = (8 - y + z)/3, y = (-1 + 2*z + x)/3, z = (10 - x + 2*y)/3
Let us initialize all the variables as 0, and then proceed with iterations. So we first run the three commands x = 0, y = 0, z = 0. Then we run the three commands x = (8 - y + z)/3, y = (-1 + 2*z + x)/3, z = (10 - x + 2*y)/3 one by one.
After this, we go for the 'Re-Run Part of Command-History' option (as we now have to just run the last three commands, in a queue, again and again as per the prescription of the Gauss-Seidel iteration method). So, now we click at the Re-Execute a Defined Part of Command-History button (or press the equivalent hotkey Alt+E). We now find that the 'Wizard for Generation of the Re-Run = Commands Syntax' has appeared. With the help of this wizard, we choose the command x = (8 - y + z)/3 as the starting command, then choose the command (i.e., the next to next command) z = (10 - x + 2*y)/3 as the ending command, and then choose a halting time of 1 (one) second between successive commands. Now we click at Finish, and find that a Assam-Calcu 'Re-Run' command of the form 'Re-Run = Commands ranging from number 00000017 to number 00000019 (total 003 commands) haltingly' has appeared. We now click at the 'Run Above Command' button, and view the halting display of the three answers (for the first iteration).
Again we are to click at the same button to see another set, then again another, and so on --  till the values of the unknowns x, y & z become practically steady! We thus find that after 35 number of re-run operations we arrive at the following final values for x, y & z:
x = 3.00000000000,    y = 4.00000000000,    z = 5.00000000000, which comprise just the exact solution; while only after 11 re-run operations the results are quite close to the exact solution, i.e.,:
x = 3.00010986025,    y = 3.99943728401,   z = 4.99958823593.
Note: To jot down on paper (or to copy into the clipboard) the aforesaid multiple-variable values, it's advisable to click EITHER at the Show Session Report button so as to open the Session Report OR better at the List Variables button to view just the present values of the variables (i.e., of x, y & z).

6. Calculating (as per simple LCAO-MO theory involving only an 1s-type AO-pair with a single orbital exponent variable k) the internuclear potential energy U of hydrogen molecular ion (H2+ ion) as a function of its internuclear distance R:
As is nicely explained in Ch. 3 (Section: MO Theory of H2+ molecular ion) of Quantum Chemistry by Ira N. Levine (3rd Ed., Prentice Hall of India, New Delhi, 2003), the internuclear potential energy U (which is also the electronic energy including internuclear repulsion VNN) of the ground electronic state of H2+ ion (as per the aforesaid simple MO theory) is expressible by the following straightforward relations:
Internuclear Potential Energy  U = (Haa + Hab)/(1 + Sab) + 1/R
where
Overlap integral    Sab = (1 + k*R + k*k*R*R/3) * exp((-1)*k*R)
Coulomb integral    Haa = 0.5*k*k - k - 1/R + (k+1/R) * exp((-2)*k*R)
Resonance Integral  Hab = (-0.5)*k*k*Sab - k*(2-k)*(1+k*R)*exp((-1)*k*R)
[Here k is the optimum orbital exponent for a given distance R, obtainable via variation theory using a computer-program such as the one developed by this author and freely available from his site (it is also included within the working folder of Assam-Calcu). The program output displaying the (R, k) values ranging from (0.4, 1.8327) to (8, 1.0000) in steps of 0.2 atomic unit (a. u.) in R is as listed in the file INPE_Res.txt.] It may be noted here that from the result of the above straightforward calculation, pretty realistic values of the (equilibrium) bond-length Re and equilibrium bond-dissociation energy De for H2+ ion could be easily obtained.
To do this above calculation very quickly using Assam-Calcu, first enter the commands R = 0.4 and k = 1.8327 therein. Then enter the above three expressions for Sab, Haa and Hab one by one. Then enter the expression for U, getting hereby the value of U for R = 0.4. Next, put R = 0.6 and the corresponding appropriate value for k (it is 1.7262) into Assam-Calcu, and then just re-run the last four commands (the appropriate re-run command may be generated by invoking the corresponding wizard) for values of Sab, Haa, Hab and U. The new value of U for R = 0.6 is thus obtained. Repeat the above process (the same re-run command may be just recalled and used, there's no need to invoke the wizard again) for all other values of R (up to 8.0) for which k is available in the aforesaid file-list.

Note: To jot down current values of the variables (R, k, Sab, Haa, Hab, U) better click at the List Variables button.

01. I know that we may run Assam-Calcu by double-clicking at the desktop icon named 'Assam-Calcu - Prog-able All-P'. But in my case, where is that desktop icon?
I'm sorry that in your case the Assam-Calcu Installer was unable to copy the shortcut (link) icon (file) to your Windows desktop -- for most of the computers it succeeds! But you may easily do that yourself. To do this yourself, open the working folder (e.g., C:\AssamCalcu), starting from, say, 'My Computer'. From that working folder find and copy the link-file named 'Assam-Calcu - Prog-able All-P' (see picture of that link-file below), and then paste that link-file to your 'Windows desktop' to facilitate running the Assam-Calcu application in future.

02. I keep getting an error message: 'Row or column position is off the screen!' whenever I try to run (i.e., open) Assam-Calcu. Where is the problem?
Most probably your monitor (VDU) screen resolution (screen area in Windows terminology) is not set to a level high enough (i.e., at least to a level of 800 by 600 pixels). You may try improving this particular Windows setting (via Control Panel - Display), or as a simpler option may also try changing the aforesaid desktop-icon's properties to have Assam-Calcu always run in 'full-screen (i.e., maximized) window' mode - this solution also generally works.

03. Can't all such calculations be done via writing some programs, say in FORTRAN or in BASIC?
Why not? But, is learning full-fledged programming an easy job? Assam-Calcu resides in the twilight zone, i.e., a no-man's-land, between Using a Calculator and Doing Programming! So, it offers the benefits of programming even to lay users with a very little knowledge of programming, and thus slowly & unknowingly initiates people to the ideas and concepts of computer-programming! [Also, besides, the less we talk about the precision and the range of values for calculations in FORTRAN or BASIC, the better it is!]

04. What? Can it also help us learn computer-programming?
Surely. The more someone would use Assam-Calcu, particularly via defining and manipulating variables, the more would he or she feel at home with the basic ideas in computer-programming. In fact, the 'Assam-Calcu History Commands-Listing' obtainable from the Assam-Calcu 'History Re-Run' command is itself almost a FORTRAN program!

Yes, surely. Just type an && sign after the command, and type any comment portion beyond this double-ampersand sign.

06. How to preserve a session report for future reference?
The session report, ordinarily, lasts only for the duration of the particular session. To preserve it for future use, click at 'Session Report' to display the same, then from File menu, click at 'Save As', then save this report with a different name OR in a different folder. (Such a saved report may be viewed with Notepad or with WordPad etc.)

07. Isn't there a difference between integer and real variables, as in FORTRAN?
Thank God, there's none! (Have you checked the tutorials?) In FORTRAN, if we write k = 1.381E-23, k will become simply zero. But NOT here. So, don't worry here about this issue.

08. Should we write here 2 as 2.0, as in old FORTRAN versions?
Not necessarily, again for the same reason mentioned just above.

09. How to backup the command-history?
The command-history resides in the file named Comm_Hist (exactly speaking, named Comm_Hist.dbf) in the working folder (generally, the folder C:\Assam_Calcu). So, to backup the command-history, just backup this particular file (say, to a removable pen-drive). When your hard-disk fails, first re-install Assam-Calcu, then copy this file back into the Assam-Calcu working folder.
Note: The similar addition-history of the inbuilt Assam-Adder resides similarly in the file named Addn_Hist (exactly speaking, named Addn_Hist.dbf) in the same working folder -- if this file exists, back up this too.

10. Why can't I change the Assam-Calcu command-history? Can I renew (i.e., reset) it?
Why, history shouldn't be changed, isn't it? But you may surely erase the entire command-history at one go, if you really feel   over-burdened with this heritage of command-history! To do that, just delete the above-mentioned file (Comm_Hist.dbf) - you'll see that your command-history has been renewed, i.e., got reset.

11. Within the middle of a multi-step calculation job, I unknowingly closed down Assam-Calcu! Without repeating the earlier (i.e., already done) steps one by one, is there a faster way through which I may recover the continuity of working on that multi-step job, and then happily continue working on the remaining part of that calculation project?
Yes, surely! In this situation, just generate (using the aforesaid wizard for Re-Run syntax generation) the appropriate re-run command for re-running the old commands of the lost last session in one go, and then just run that re-run command. The automated re-running process would now take only a few seconds. After that, you may happily continue working on the remaining part of the long calculation project!

12. Why can't I exit from the calculator if some report, data or help is being displayed?
Because someone may actually want to only hide the display of that report etc., but may instead unintentionally close the whole application! So, if you want to exit from Assam-Calcu, first close any report (or data) window, and then try to exit!

Cite use of this package as:
Assam-Calcu: A Programmable All-Purpose Calculator 3.1, © 2009 Rituraj Kalita, Guwahati (India).

References:
See the inbuilt list of constants & conversion factors.