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and use the remainder of the instruction manual as reference as and when needed. The main bulk of the book is for the novice, explaining clearly and concisely all the statements and commands. Most of the chapters are essentially a 'hands-on' teaching programme in 2X81 BASIC, with a number of useful exercises to extend the knowledge gained in the preceding text. Chapters 26, 27 and 28 introduce the idea of machine code, the organisation of the memory, and explain what the system variable are and where they are stored. Appendix A lists the character set, Appendix B gives the Report (Error) codes and Appendix C give a short r6sum6 of the ZX81 and its individual characteristics under the heading: "The ZX81 for those that understand BASIC". The Index is useful and comprehensive, giving not only page references but also the key sequences required for all keywords and shifted characters. Those who already have some knowledge of BASIC will note from the command/statement list that there are a few common BASIC commands that are noticeable by their absence, principally DATA, READ, RESTORE, ON-GOTO, LEFT$, MID $, RIGHT $ and TL$. These are listed in the index but not in the bold type, indicating that they are ZX81 keywords. Although the ZX81 does not have these commands, the manual explains the use of simple routines to obtain access to the first four effectively. The latter four deal with string manipulation, and whereas the ZX81 does not have these specific commands the way in which it deals with strings is comprehensive, albeit nonstandard. It uses a notation called 'slicing' for describing substrings. This can be applied to arbitrary string expressions and takes the general form . . .'string expression (start TO finish)' so that "ABCDEF" (2 TO 5) = "BCDE" Review and "ABCDEF"(3) = "C" Different as this may be from other common micros it is easily understood and will readily yield the results you would expect from the more usual string commands. using it In use, the ZX81 presents no real lasting problem to operate. If you are new to using a computer then you have probably used a calculator and so the keyboard spacing wilt not seem all that different. If, on the other BETS ••£) BEsS HESS MS3 £2 lira Ha Qg EE) bdJ 0 0 Qg 0 0 | SB BH PR 183 EB HS CS EB IB = \ . ;- -A\ *.* »•.:• t?OF -.£.. A.-: v K^ o O * ^ ^ jOSUB ^AC ^ ^ K3Ea Mi^fffli •GEl BQBE3) M^Q 01El 0 : uB nil hh B0 Elj CU EH • a \ ic; - ap~ .at ,E\ ."-• '..i \E*T PAfSt hand, you regularly use a typewriter keyboard, you will take a few hours to adapt to the diminutive size of the ZX81: but then those few hours will enable you to become accustomed to the fact that some keys may give up to six different results! One very small but important improvement on the ZX81 is its rubber feet. The ZX80 and ZX81 are both very light in weight, and with its new feet at least the ZX81 does not skate all over the table as you use it I All in all, I can recommend the ZX81 to any intending purchaser — it is very good value for money. It does not have the facilities one would require for a business machine but anyone wanting to learn personally what a computer can do, without initially spending a fair amount of money, should seriously consider one. After all, the ZX81 does not cost much more than the cassette recorder that you will need to buy for some makes of micro. The only personal drawback to the whole Sinclair ZX episode is that my sevenyear-old son tends to look upon the ZX80 and the ZX81 as more his size! He does not have quite the reverence for the ZXs as he does for other micros of the desktop variety. Demand for its use seems to be unending and we often hear "Press NEWLINE, silly!" as he instructs his five-yearold sister in the uses of twentieth-century technology. \mm IB1 i
SYSTEM/MULTIFUNCTION COMMANDS BREAK CLEAR CLS CONT COPY EDIT FAST FUNCTION GRAPHICS LIST LLIST LOAD LPRINT NEW NEWLINE PAUSE RUBOUT RUN SAVE SLOW STOP STATEMENTS ABS ACS AND/OR,NOT ASN AT ATN CHR$ ZX COMPUTING SUMMER 1982 Review Halts run and returns to command mode. Deletes all variables, freeing the space they occupied. Clears screen — clears display file. Continues STOPped program. Sends copy of display to printer. Returns current line (indicated in program list) to bottom of screen for editing. Starts fast mode. Display file is displayed only at end of program, while INPUT data is being typed in or during PAUSE. Returns alternative keyword set. Returns alternative character set. Lists specified line(s) of program on screen. Like LIST but using printer instead of screen. Looks for specified program on tape — loads it and its variables. Like PRINT but using printer instead of screen. Clears memory and awaits new program. Enters command as statement. Stops computing and outputs the display file to the screen for specified time, or until another key is pressed. Deletes character to left of cursor. Executives current program. Writes specified program to cassette interface. Records program and variables. Puts computer into compute and display mode, in which the display file is displayed continuously. Stops a program that is RUNning. Returns absolute value of specified variable. Returns arcosine (in radians). Comparative tests. Returns arcsine (in radians). Defines position of next PRINT statement (in screen lines/columns). Returns arctangent (in radians). Gives character whose code is specified. CODE Gives code of the first character in specified string. COS Returns cosine of angle (in radians). DIM Dimensions array size. EXP Returns exponential of specified number. FOR Used in conjunction with TO and NEXT to execute a defined loop. GOSUB Jumps to defined subroutine. GOTO Jumps to specified program line number. IF Conditional test, used in conjunction with THEN followed by specified statement. INKEY$ Reads keyboard, result is character of next key pressed. INPUT Assigns value of keyboard entry to specified variable. INT Returns integer part of number (rounded down). LEN Returns length of specified string, LET Assigns specified value to specified variable. LN Returns natural logarithm of a number. PEEK Returns value of specified memory location. PI Tl{3.14159265 . . >. PLOT Blacks in pixel at specified co-ordinates. RAND Sets the seed used to generate the next value of RND. REM No effect on program, allows inclusion of text for comments. RETURN Returns to main program from subroutine. SCROLL Scrolls the display file up one line. SGN Returns sign of number. SIN Returns sine of angle (in radians). SQR Gives square root of number. STEP Used with FOR . . . NEXT loops, defining increment between loops. STR$ Returns string representation of number. TAB . Defines column in which PRINT statement will begin. TAN Returns tangent of angle (in radians). UNPLOT Like PLOT, but blanks out a pixel instead of blacking in. USR Calls machine code subroutine. VAL Evaluates a string as a numerical expression. TABLE 1
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j Summer Britain's Biggest Magazine
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ZX 80/81 HARDWARE/SOFTWARE ZX KEYBO
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ZX Computing is published quarterly
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16K-byte RAM pock for massive add-o
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The @*?$1!&£@ RAM pack Dear ZX Com
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I u < o •0 8 & £T © Benchmarks
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1 1© L" 20 30 IN5 5 0 60 80 9C 100
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The Explorer's Guide to the ZX81 IF
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Orbit S M King from Bristol takes y
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Page 73 and 74: Review Keyboard Review Crofton's Ad
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Page 81 and 82: 51 IF A(2) «* 188 THEN LET A (Z)
Page 83 and 84: 4110 IF (A(Z - 13) = 1 OR A(2 - 13)
Page 85 and 86: ZX81 HARDWARE 40 KEY KEYBOARD. Kit
Page 87 and 88: 4090 GOTO 9100 5000 GOSUB 9500 5010
Page 89 and 90: I 1K Games 10 LET 20 LET 30 LET 4-0
Page 91 and 92: Etchasketch This very short program
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Page 97 and 98: 270 280 290 300 310 320 IF IF IF IF
Page 99 and 100: Make sure you get every issue of ZX
Page 101 and 102: ZX80 Programs ZX80 fights back Musi
Page 103 and 104: Catch Avoid being trapped by your s
Page 105 and 106: Software Orwin strikes again Casset
Page 107 and 108: ZX81 Software LARGE CHARACTERS REM
Page 109 and 110: Moving graphics Getting into the Mo
Page 111 and 112: Specialist Book§ i Choosing progra
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Page 119 and 120: Compiler A program whose function i
Page 121 and 122: ZX COMPUTING SUMMER 1982 Computer G
Page 123 and 124: S-100 Name of a bus or connection s
Page 125 and 126: After taking your move the computer
Page 127 and 128: WHAT'S ON NEXT? IN HOBBY ELECTRONIC
Page 129 and 130: are not lost when the ZX81 is turne
Page 131 and 132: ZX Users' Club JOIN YOUR USERS' GRO
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