Keystroke programming

10.1What a keystroke program is#

A program is a list of keystrokes the calculator remembers. You turn on program mode, press the keys you would normally press, and each key press becomes one line. Later you run the list with one command, and the calculator presses the keys for you.

Program memory holds up to 448 lines. Each line is one command. A command like fLBLSST 1 (a label) or STO 5 is stored as one line even though it takes several key presses. A multi-digit number takes one line per digit.

Whatever is in X when the program starts is its input. Whatever is in X when it ends is its answer. A program can also use the stack, the registers and the flags.

10.2Enter a program#

1. Press gP/RR/S (P/R) to turn program mode on. The PRGM indicator lights and the display shows 000-.
2. Start with a label: fLBLSST (LBL) and then a label. A label is a digit 0 to 9, a point and a digit (.0 to .9), or one of A, B, C, D, E (√x, eˣ, 10ˣ, yˣ, 1/x).
3. Key in the steps just as you would for a hand calculation.
4. End with gRTNGSB (RTN, return).
5. Press gP/RR/S again to leave program mode.

While you record, nothing is calculated and the stack is not touched. New lines are inserted at the current line, after the line shown.

Example 10.1

Area of a circle from its radius

1. Program mode on. LBL A, then x², π, ×, RTN. Program mode off.

   gP/RR/SfLBLSST√xgx²√xgπEEX×gRTNGSBgP/RR/S

2. Key in the radius 3 and press f, A.

   3fA√x

Key in another radius and press f, A again to reuse the program. The earlier answer moves up the stack.

10.3Read the program display#

In program mode the display shows the line number and the keycode of the command, for example 001- 42,21,11. The keycodes are the row and column of each key: 42 is f, 21 is SST and 11 is √x. So 42,21,11 is LBL A. Digits show as themselves. A register such as .1 shows as .1.

Example 10.2

See the first line of a program

1. Enter the circle program, then press g, BST (g, SST) until you reach line 001.

   gP/RR/SfLBLSST√xgx²√xgπEEX×gRTNGSBgBSTSSTgBSTSSTgBSTSSTgBSTSST

Example 10.3

See where a program ends

1. Press g, R/S for program mode, then LBL A, g RTN and read the last line.

   gP/RR/SfLBLSST√xgRTNGSB

10.4Run a program#

There are four ways to start a program.

• f and then a label key from A to E (√x to 1/x): runs that label.
• GSB and then any label (a digit, a point and a digit, or A to E): runs that label as a subroutine, then returns.
• In USER mode, press a plain A to E key.
• GTO and a label (positions the program) and then R/S (R/S): runs from there.

The program runs until it reaches RTN, or until it stops at an R/S line. When it finishes, the display shows X. A program that runs off the end of memory acts as if it ended with RTN.

Example 10.4

Run a label with GSB

1. Program label 9 = add 12 to X. Then run it on 3 with GSB 9.

   gP/RR/SfLBLSST912+gRTNGSBgP/RR/S3GSB9

Example 10.5

Run it twice in a row

1. Run label A (x² + 1) on 3, then run it again on the result.

   gP/RR/SfLBLSST√xgx²√x1+gRTNGSBgP/RR/S3fA√xfA√x

10.5Stop for input: R/S inside a program#

Put R/S (R/S) in a program where it should pause. The calculator stops and shows X. Key in a number if you want, then press R/S to carry on from the next line.

Example 10.6

Pause in the middle of a program

1. Label B: ×2, R/S, +3. Run it on 5 and then continue.

   gP/RR/SfLBLSSTeˣ2×R/S3+gRTNGSBgP/RR/S5fBeˣR/S

R/S pressed from the keyboard when no program is running starts it from the current line. If the pointer is at the end, it restarts from line 000.

10.6Run labels A to E with one key#

Turn on USER mode with fUSERRCL. The plain A to E keys then run your programs. Turn it off with fUSERRCL again. See Modes.

See also Display and angle modes: USER mode

10.7Use subroutines#

A subroutine is a labelled piece of a program that another part calls. In a program, GSB and a label jumps to that label. When the subroutine reaches RTN, the program continues with the line after the GSB. You can nest subroutines up to seven levels deep (Error 5 if you go deeper).

Example 10.7

A program that calls a subroutine

1. Label B: call .2, then add 1. Label .2 multiplies by 10. Run B on 4.

   gP/RR/SfLBLSSTeˣGSB.21+gRTNGSBfLBLSST.210×gRTNGSBgP/RR/S4fBeˣ

Example 10.8

A subroutine used twice

1. Label 1 squares x. Label 2 calls it twice: x⁴. Run on 3.

   gP/RR/SfLBLSST1gx²√xgRTNGSBfLBLSST2GSB1GSB1gRTNGSBgP/RR/S3GSB2

10.8Jump with GTO#

In a program, GTO and a label jumps there for good, with no return. Use it to build loops or to skip lines. GTO searches forward from the current line and wraps around to the top if it must.

From the keyboard, GTO and a label only moves the program pointer. Press R/S to run from there. GTO CHS nnn (press GTO, CHS and three digits) moves to a line number. The line must exist, or you get Error 4.

Example 10.9

Go to a label and run from there

1. Label 1 keys in 11. Press GTO 1 to place the pointer, then R/S to run from there.

   gP/RR/SfLBLSST111gP/RR/SGTO1R/S

10.9Make decisions with tests#

A test checks X (and sometimes Y). In a program, if the test is true, the next line is run. If it is false, the next line is skipped. The test keys are gx≤y÷ (x≤y) and gx=0× (x=0), and gTEST− (TEST) followed by a digit.

Example 10.10

The larger of two numbers

1. Label E: if X ≤ Y then swap. Key in 3, ENTER, 7 and run it.

   gP/RR/SfLBLSST1/xgx≤y÷x⇄ygRTNGSBgP/RR/S3ENTER7fE1/x

Example 10.11

The larger of two numbers, the other way round

1. Same program, key in 7, ENTER, 3.

   gP/RR/SfLBLSST1/xgx≤y÷x⇄ygRTNGSBgP/RR/S7ENTER3fE1/x

Example 10.12

Absolute value with a test

1. Label 6: if X < 0 then change sign. Run it on −5.

   gP/RR/SfLBLSST6gTEST−2CHSgRTNGSBgP/RR/S5CHSGSB6

Example 10.13

Branch on zero with x=0

1. Label 4: if X = 0 then GTO 5, else return 1. Label 5 returns 2. Run on 0.

   gP/RR/SfLBLSST4gx=0×GTO51gRTNGSBfLBLSST52gRTNGSBgP/RR/S0GSB4

10.10Flags in programs#

gSF4 and a digit sets the flag, gCF5 and a digit clears it, and gF?6 and a digit (F?) is a test: if the flag is set, the next line runs; if not, it is skipped. A flag keeps its state after the program ends, so a program can remember things between runs.

Example 10.14

Flag set: the program changes the sign

1. Label 7: if flag 3 is set then CHS. Set flag 3 first, key in 5 and run label 7.

   gP/RR/SfLBLSST7gF?63CHSgRTNGSBgP/RR/SgSF435GSB7

Example 10.15

Flag clear: the program skips the line

1. Same program without setting flag 3.

   gP/RR/SfLBLSST7gF?63CHSgRTNGSBgP/RR/S5GSB7

Remember that the line skipped is one line. A number like 10 is two lines, so skipping it only skips the 1.

10.11Loops: DSE (decrement and skip)#

A loop repeats lines. fDSE5 (DSE) and a register decrease the number in that register and skip the next line when it has counted down to its limit. A counter written as nnn.xxxyy holds the count nnn, the limit xxx (after the point) and the step yy. With a plain whole number such as 5, the limit is 0 and the step is 1. DSE steps 5, 4, 3, 2, 1, 0 and skips when the count reaches 0 or below.

Example 10.16

Add up the numbers 1 to 5

1. Label C: 5 → R0, 0 in X. Label 1: add R0, DSE 0, go back to label 1. RTN. Run C.

   gP/RR/SfLBLSST10ˣ5STO00fLBLSST1RCL0+fDSE50GTO1gRTNGSBgP/RR/SfC10ˣ

Example 10.17

Factorial with a loop

1. Label B: STO 0, put 1 in X. Label 1: multiply by R0, DSE 0, loop. Run on 5.

   gP/RR/SfLBLSSTeˣSTO01fLBLSST1RCL0×fDSE50GTO1gRTNGSBgP/RR/S5fBeˣ

10.12Loops: ISG (increment and skip)#

fISG6 (ISG) and a register increase the counter and skip the next line when it passes the limit. In 1.004 the count starts at 1, the limit is 4 and the step is 1 (the digits after the point are the limit xxx and the step yy). The loop runs for 1, 2, 3 and 4.

Example 10.18

Sum of squares 1² to 4²

1. Label D: store 1.004 in R1, put 0 in X. Label 2: RCL 1, INT, x², add, ISG 1, GTO 2, RTN. Run D.

   gP/RR/SfLBLSSTyˣ1.004STO10fLBLSST2RCL1gINTSTOgx²√x+fISG61GTO2gRTNGSBgP/RR/SfDyˣ

Example 10.19

Watch the counter move

1. Store 1.003 in R1, then press ISG 1 and recall it, twice.

   1.003STO1fISG61RCL1fISG61RCL1

10.13Indirect addressing in programs#

The I register can choose a register or a label. GSB or GTO followed by TAN jumps to the label named by the number in I: 0 to 9 give labels 0 to 9, 10 to 19 give .0 to .9, and 20 to 24 give A to E. A negative I in GTO goes to that line number. STO (i) and RCL (i) use R(i), as described in Memory.

Example 10.20

Choose a label with I

1. Label A is x² + 1. Store 20 in I (label A) and run GSB I on 3.

   gP/RR/SfLBLSST√xgx²√x1+gRTNGSBgP/RR/S20STOTAN3GSBTAN

Example 10.21

Loop through registers with (i)

1. Store 7 in R3 and 3 in I. Key in 0 and recall R(i).

   7STO33STOTAN0RCLCOS

10.14Edit, step through and clear programs#

In program mode, SST moves the pointer to the next line and gBSTSST (BST) moves it back. ← deletes the line shown. New keys are inserted after the line shown. GTO CHS and three digits jump to a line, for example 003.

Example 10.22

Delete a wrong line

1. Enter 1, 2, then delete the last line with the back arrow.

   gP/RR/S12←

Example 10.23

Jump to a line

1. Enter LBL A and the digits 1 and 2, then jump to line 001.

   gP/RR/SfLBLSST√x12GTOCHS001

fCLR PRGMR↓ (CLEAR PRGM) in program mode erases the whole program and goes to line 000. Outside program mode it only moves the pointer to line 000. Use it before entering a fresh program.

Example 10.24

Clear the program

1. Enter some lines, then press f, CLEAR PRGM.

   gP/RR/SfLBLSST√x12fCLR PRGMR↓

Not every key is recorded. These act at once instead: P/R, SST, BST, ←, CLEAR PRGM, PREFIX, USER and MEM.

10.15Run a program one line at a time#

Outside program mode, SST runs the next program line and shows the result. Use GTO and a label first to put the pointer at the start. Press SST again for each line. This is the best way to find a mistake: you see what each line does to X.

Example 10.25

Step a program

1. Label 3 keys in 1, adds, then squares. Go to label 3, key in 3 and press SST three times (1, then +, then x²).

   gP/RR/SfLBLSST31+gx²√xgRTNGSBgP/RR/SGTO33SSTSSTSST

10.16Limits of programs#

• Program memory is 448 lines. A full memory gives Error 10 when you try to add another line.
• Subroutines nest up to 7 levels. A deeper call gives Error 5.
• A program that runs for a very long time (about a million steps) is interrupted so the app does not freeze.
• An error inside a program stops it and shows the error.
• A missing label gives Error 4.

Example 10.26

A runaway program is stopped

1. Label 8 calls itself forever. Run GSB 8.

   gP/RR/SfLBLSST8GSB8gP/RR/SGSB8