WAR GAMES, it seems, are forming part of the Sinclair users' staple games diet. Two recent offerings include the opportunity to be an aircraft gunner, zapping enemy aircraft out of the sky, and of controlling a naval task force sent to deliver a far-off island from enemy occupation - no prizes for guessing from where that idea arose.
The first, Night Gunner, casts you as a rear gunner in the turret of a bomber, firing at enemy fighter aircraft which weave about the screen. Good, clear graphics represent the enemy aircraft and a cross in the centre of the screen is the gunner's sights. Each time you are hit by enemy aircraft, resulting in the loss of one of your three lives, the HIT flashes on the full screen, somewhat reminiscent of the scoreboard at an American baseball game.
The cassette, a 16K game, costs £4.95 and is available from Digital Integration, Hampshire, and will also soon be available from retail outlets.
The chance to control even more fire power is presented in Naval Blockade. As commander of a task force sent to retake an occupied dependency, you have an aircraft carrier with five aircraft, a troop carrier and four frigates.
The idea is to land your troops on the island, which is at the centre of a 10 x 26 grid, having fought-off enemy attacks. The graphics in this 16K game are simple but clear, and movement is achieved by entering a series of co-ordinates and typed instructions.
Naturally, damage factors have to be coped with and missiles are not inexhaustible, particularly since the enemy bases are close to the island but you have the occasional advantage of intelligence reports.
Naval Blockade is from Hewson Consultants, Oxfordshire for £5.95.
FLIGHT SIMULATION and related subjects seem to be reasonably popular, especially now that most personal computers can use high-resolution graphics. Fighter Pilot, however, is not for a computer with such facilities but for the ZX-81 with 16K RAM.
The idea is that you are a fighter pilot taking-off and returning to your base. You are given two options at the beginning of the program, either to take-off and fly around, then land, or to try to land on the runway.
All that sounds simple but it is very difficult, because you are flying blind. The display for the simulation is just a series of boxes with monitor readings in them. It takes a long time to get used to them.
The game is a little dull but the simulation is interesting. Fighter Pilot is available from Digital Integration, Hampshire. It costs £5.95.
MOVING FROGS across a busy road and fast-flowing river into their homes can be a hazardous business. The DJL Software game Frogger is a fairly straightforward obstacle-avoidance trek from the bottom of the screen to the top, where five frog homes await their occupants.
The journey is aided by handy logs and turtles in the river on to which the frogs can jump but beware staying too long on the turtles - they have a habit of diving and that is the end of your frog.
Points are earned for each frog which reaches home and the arrival of all five leads to increased hazards - including more traffic on the road, alligators and snake patrols on the river banks - for the next game. The hazards continue to increase two more levels, so life for the frogs becomes more and more precarious.
The cassette costs £5.95 from DJL, Wiltshire.
MACHINE CODE is becoming more popular as the personal computer market expands. The reason seems to be that Basic is very slow to use and fast interactive graphics games are not possible without using machine code. The new Artic Computing ZX Assembler aims to make the job of compiling machine code easier for beginner and expert alike.
The program is written in machine code and can be called from Basic. It is possible, therefore, to program in Basic without losing the assembler from memory.
The code to be assembled is put into a REM statement at the beginning of the program. The code can be written in the standard Z-80 mnemonics. Ordinary text which is to be printed on to the screen can be written directly into the assembly code and will be turned automatically into hexadecimal.
A useful command which can help to debug machine code programs is display and modify machine registers. The registers are where the machine does much of its processing work and by seeing which numbers are in the registers after program execution it is sometimes possible to tell what is going wrong inside the machine code routine.
The ZX Assembler is sold by Artic Computing and costs £9.95.
ASTEROIDS is a fairly standard game on the ZX-81 and many software houses have produced a version. The Software Farm has now jumped on to this bandwagon and produced its version.
The graphics of the game are fairly chunky but the action is very smooth. The screen has a wrapround effect, so that as well as being able to spin around in space your ship can move forward. It will disappear from one side of the screen and reappear at the other.
If you fire when the ship is off the screen or just about to disappear, a very strange effect occurs. You press the fire button and the laser beam, shot from the nose of your ship, continues off the edge of the screen and appears on the other side. That effect is on several versions of the game at present available and it seems to be a disadvantage of having a wrapround screen.
Apart from that, the game is reasonably fast and the asteroids are very difficult to miss, as they break-up after you have fired at them, only to fly back in the face of your ship.
Asteroids is sold by The Software Farm, Gwent, and costs £5.95.