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E0001 Computers in Engineering

E0001 Computers in Engineering. Built in Functions. General Notes. Error in Assignment A-E & M-R - TYPO Volume should be 152.13, 22.44, 5.77 Assignment S-Z constant = 2.749*10 -8 Assignment 2 due 9 April but …. submit until 12 April Ass1 and 2 handed back after holidays.

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E0001 Computers in Engineering

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  1. E0001 Computers in Engineering Built in Functions

  2. General Notes • Error in Assignment A-E & M-R - TYPO Volume should be 152.13, 22.44, 5.77 • Assignment S-Z constant = 2.749*10-8 • Assignment 2 due 9 April but …. submit until 12 April • Ass1 and 2 handed back after holidays..

  3. Readings and Exercises • Schneider Section 3.4 p 72-78 • Schneider Practice Problems 3.4 p 78; programming problems #’s 57, 60, 62, 66, 68

  4. Rem statements • Rem short for REMARK • used for adding comments to code • useful for the programmer, not the user • non executable line • Two ways of adding comments • REM • ‘

  5. Examples REM this line is a comment REM This program will calculate…. REM This program was written by…. INPUT r,b,h ‘radius, base, height READ n$, no$ ‘name, number

  6. Numeric Functions • covers common numeric and trigonometric terms • square root - SQR(x) • SIN(angle), COS(angle), TAN(angle) • BEWARE - (angle) must be in RADIANS • LOG (x) • see handout for more examples

  7. Examples of Numeric Functions • SQR (x) - square root of x where x is • variable - given a value by the program or the user • arithmetic operation - (6-4)/360*12 • ABS - absolute value • ABS(-3) = 3; ABS(7) = 7 • ABS(SQR(CINT(x)))

  8. String Functions • allows examining strings or parts; combining strings • allows string comparisons using <, >, = (relational operators)

  9. Examples of String Functions • LEN(s) - s is known as the argument • returns the length of the argument i.e. the number of characters contained in the argument • blanks are counted as characters • LEN(“John and Mary”) = 13 • Z$ = “John and Mary”: LEN(Z$) = 13 • IF LEN(Z$) = 20 THEN PRINT “HELLO”

  10. LEFT$(x$, n) - x$ is any string; n is an integer from 0 to LEN(x$) • x$ = “John and Mary” • PRINT LEFT$(x$,4) - gives the output John • see also MID$(x$,n,m) and RIGHT$(x$,n) • LCASE$(X$); UCASE$(X$); INSTR(n,X$,Y$) • VAL(X$) - converts a string whose contents represent a number to its numerical form. • ignores leading blanks • converts a string up to its first nonnumerical character into its numerical value.

  11. Built-in Functions • prewritten “subroutine” that does one operation • returns ONE value only • implimented by arithametic statement • variable = equation • designed to manipulate both numerical and string data • cover common calculations

  12. Computers in Engineering PRINT USING STATEMENT

  13. Overview In a circuit three currents are represented by the variables cur1, cur2, cur3 Plan and write a program to input these values and calculate and display the average current

  14. Plan • Outputs… • Inputs…. • Process… • flowchart/plan/pseudocode

  15. INPUT statements Write input statements to enter these variables INPUT “current 1”, cur1 INPUT “current 2”, cur2 INPUT “current 3”, cur3

  16. In Memory User enters 9.16, 12.4, 0.9 cur1 9.16 cur2 12.4 cur3 0.9

  17. Calculate total and average currents and print totCur = cur1 + cur2 + cur3 AvgCur = totCur / 3 PRINT , cur1 PRINT , cur2 PRINT , cur3 PRINT , “________” PRINT , TotCur PRINT “Average”, AvgCur

  18. Qbasic Screen

  19. To add units to a variable PRINT “Current”; cur1; “amps” PRINT “prompt” ; variable list ; “prompt”

  20. PRINT USING • PRINT USING statement can be used instead of PRINT to make decimal points line up • has general form - PRINT USING “format string”;expression list e.g PRINT USING “ ##.##”; cur1

  21. Format string • String of characters • letters, numbers, punctuation • some have special meanings • if no special meaning qb will simply display it on the screen • if has special meaning qb uses it to determine the format for displaying one of the expressions in the list

  22. Formatting numbers • # # #.# # • displays 3 digits preceding the decimal • fewer than 3 before qbasic leaves a space • more than 3 - will be displayed correctly but in a different format, will also precede it with a % character • displays 2 digits after the decimal • fewer than 2 - displays zeros for the missing digits • more than 2 - displays the rounded value

  23. Format string Fmt$ = “current is ##.## at ###.# volts” PRINT USING Fmt$; cur; volts c.f. PRINT USING “format string”;expression list

  24. Scientific notation - e.g. 2E-6 • ^^^^ • represent positions for E, minus or plus sign, two digit exponent • ^^^^^ • for double precision numbers • represent positions for E, minus or plus sign, three digit exponent • e.g. FMT$ = “current is ##.###^^^^ at ##.#### ^^^^ volts”

  25. Output? Current is 23.5, volts are 117.6 FMT$ = “current is ##.###^^^^ at ##.####^^^^ volts” Current is 2.350E+01 at 1.1760E+02 volts • additional strings can be added • FMT$ = “current is & ##.###^^^^ at ##.####^^^^ volts” • curType$ = “direct” • PRINT USING Fmt$; curType$; cur; volts Current is direct 2.350E+01 at 1.176E+02 volts

  26. Take a break Return for assignments

  27. Write a program to convert a US customary system length in miles, yards, feet and inches to a Metric System length in kilometres, meters and centimetres. After the number of miles, yards, feet and inches are requested as input, the length should be converted entirely to inches and then divided by 39.37 to obtain the value in meters. The INT function should be used to break the total number of meters into a whole number of kilometres and meters. The number of centimetres should be displayed to one decimal place. Some of the needed formulas are: Total inches = 63360 * miles + 36 * yards + 12 * feet + inches Total meters = total inches / 39.37 Kilometres = INT (meters/1000)

  28. Kepler's Third Law states that for objects with an elliptical orbit (such as satellites orbiting Earth or planets orbiting the sun), the square of the Period is proportional to a3, where a is half the length of the major axis of the ellipse. For nearly circular satellite orbit above Earth, a can be approximated by the radius of the earth plus the altitude of the satellite. Thus • a ~ 6378 kilometers + altitude • If the Period is expressed in minutes and the length of the major axis is expressed in kilometers, then • Period 2 = 2.749E-8*10-4*a3 • Write a program to produce the table shown below. The information in the first two columns should be stored in DATA statements and the period should be computed and displayed to an appropriate number of decimal places. Type of Satellite Altitude (km) Period (minutes) Earth imaging 400 Low-altitude communications 1500 Geosynchronous communication 35789

  29. The general law of perfect gases states that PV / T = n R = constant • where • P is the gas pressure (in atmospheres), • V is the volume (in litres), • T is the temperature (in degrees Kelvin), • n is the number of moles, • R is the constant of perfect gases (0.82 Liter-atm/Kelvin-mole).

  30. Write a program to produce the table for the case n=1 thus giving V = RT/P. The user with an INPUT statement should enter a temperature (in Celsius) and pressure. Two new temperatures (in Celsius) should be calculated from the original, one increased by 500 and one decreased by 500. A corresponding pressure for each new temperature should be entered by the use of an INPUT statement. The temperature in Kelvin and the Volume should be calculated for the three temperatures and displayed. A sample output is shown below:

  31. Temperature Pressure Temperature Volume • (Celsius) (atm) (Kelvin) (liter) • 150 2.280 423 152.13 • 200 17.287 473 22.44 • 250 74.375 523 5.77

  32. Problem • The period P of a pendulum of length L and maximum displacement angle  is given by the formula P = write a program that requests as input the length and maximum angle of displacement, and displays the period of the pendulum

  33. Tutorial 1. What will be the contents of x after the following statement is executed? LET x = SQR((9 + 7) / ( 4 * 2) + 2) 2. Suppose num = 123.4567. What is the output? LET num = INT(100 * num + .5) / 100 PRINT num

  34. 3. What output is generated by the following statements (show the output EXACTLY as it would appear on the screen)? PRINT SQR (3^2 + 4^2) PRINT MID$ ("Milkshake", 5, 5) PRINT UCASE$ ("123jump") 5 shake 123JUMP try this for yourself

  35. 4. The following statements are valid. (T/F) LET H$ = "Hello" LET a$ = INSTR(H$, 3) 5. Given the data in the variable y$ shown below, which of the following statements will assign the value ALL to x$? LET y$ = "WHEN ALL ELSE FAILS, READ THE DIRECTIONS" (a) LET x$ = MID$(y$, 6, 3) (b) LET x$ = INSTR(6, y$, "ALL") (c) LET x$ = LEFT$(y$, 3) (d) LET x$ = MIDDLE$(y$, 6, 3) (e) LET x$ = RIGHT$(y$, 8)

  36. 6. What will be displayed when the following program is executed? LET a$ = "THE WHOLE" LET b$ = "PART" LET c$ = MID$(a$, SQR(4), LEN(b$)) PRINT c$ END

  37. The End

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