In demo mode, ERIC bases his every move on where little boy no. 11 is and what he's doing (see the routine at F5DA). This important role means that little boy no. 11 is in all of ERIC's classes (if he weren't, ERIC would be guilty of truancy in demo mode). In fact, little boy no. 11 is the only character besides EINSTEIN who joins ERIC for every class.

One consequence of this devotion to little boy no. 11 is that ERIC can sometimes be seen going from one end of a staircase to the other three times in succession, as if unsure of where to go. This happens because when little boy no. 11 starts climbing a staircase, ERIC will run to the top and get there before him, then run down to the bottom looking for him, and finally run to the top again to catch up with him.

The tune that plays just before a game (or demo mode) starts, and also when ERIC goes up a year, is Girls and Boys Come Out To Play. The tune that plays when ERIC makes the final shield flash, and when he opens the safe, is Au clair de la lune.

The version of Skool Daze that was released by Alternative Software Ltd in 1987 contains three visible differences from the version released by Microsphere in 1984.

(1) MR WITHIT's blackboard message at E800 reads 'WHY IT RAINS IN MANCHESTER' (which doesn't fit on the blackboard) instead of 'MANCHESTER MONSOONS'.

(2) The font graphic for the '/' (slash) character is slightly broken:

instead of

(3) In the stampede playtimes (lessons 0xFC and 0xFD), the stampede leader (little boy no. 1) walks up and down only 7 times instead of 40 while waiting for his comrades to join him.

Note that (1) and (2) appear to be regressions, which suggests that the version released by Alternative is based on an earlier cut of the code than the version released by Microsphere.

The '\' (backslash) character in the Skool Daze font has a bit missing:

Interestingly, the corresponding bit is also missing from the '/' (slash) character in the version of Skool Daze that was released by Alternative Software in 1987 (see Alternative differences), but it is present in the original 1984 release by Microsphere.

If a teacher is conducting a class without ERIC, or is conducting ERIC's class but has chosen not to engage in a question-and-answer session with EINSTEIN, he will pace up and down in front of the blackboard (or map). But the number of paces up and then down depends on the room he's in.

If he's in the White Room, he will take one pace up and then down, oscillating between x-coordinates 29 and 30. If he's in the Reading Room, he will also take one pace up and then down, oscillating between x-coordinates 45 and 46. And if he's in the Map Room, he will once again take one pace up and then down, oscillating between x-coordinates 61 and 62. But if he's in the Exam Room, he will take three paces up and then down, oscillating between x-coordinates 44 and 47.

The reason for this discrepancy in pace numbers is the method used to calculate the teacher's next pace-up or pace-down destination, which is to take his current x-coordinate and do an XOR $03 on it: see the sections of code at 7D73 and F3DD.

ERIC can usually throw a punch or fire his catapult and be confident that the impact will send one of the kids or teachers tumbling. However, on certain occasions, certain characters are invulnerable to ERIC's violence. Those characters and occasions are as follows:

• MR WACKER, when he's looking for ERIC after EINSTEIN has told him what ERIC's up to
• MR WACKER, when he's looking for ERIC after finding the pea-shooter on the fire escape
• MR WACKER, when he's looking for ERIC to send him home after accumulating 10000 or more lines
• MR ROCKITT, when he's looking for ERIC to send him home after catching mumps from ANGELFACE
• Little boy no. 10, when he's looking for ERIC to tell him about ANGELFACE, EINSTEIN or BOY WANDER in one of the special playtimes (0xF3, 0xF4, 0xF5)

The reason these characters are invulnerable while looking for ERIC is that they are under the control of the uninterruptible subcommand routine at F79E.

In addition, any boy is invulnerable when he's looking for a seat in a classroom, because he's under the control of the uninterruptible subcommand routine at 6C7C.

On those occasions when MR WACKER, MR ROCKITT or little boy no. 10 is looking for ERIC to deliver a message, ERIC can delay delivery of the message by making sure that he is writing on a blackboard when the messenger arrives. The messenger will then wait until ERIC has finished scribbling before commencing delivery.

To verify this, use the following POKEs (which make every playtime the 'special' playtime in which little boy no. 10 will come looking for ERIC to tell him that EINSTEIN is going to grass him up to MR WACKER) and then head for the nearest blackboard:

If you're feeling very patient, you can use this stalling technique to avoid having to take part in the special playtime: just stand at the blackboard for about 20 minutes until the bell rings.

Rather more interesting is that you can use this technique to avoid expulsion.

The sprite graphic data is split between two base pages: page 0xB9 for the boys and the catapult pellet, and page 0xC9 for the teachers (see 6D0A). However, the graphic data based in page 0xB9 contains exact copies of most of MR WACKER's sprites:

0xB9		0xC9

This suggests that the original plan was to have the graphic data for every character based in page 0xB9, but space ran out while adding MR WACKER's sprites, so the graphic data for him and the other teachers had to go to page 0xC9.

The copies of MR WACKER's sprites based in page 0xB9 show a slight difference in animatory states 0x51 and 0xD1 compared to the official sprites based in page 0xC9:

0xB9		0xC9
0x51	0xD1	0x51	0xD1

Note the incorrect tile at the bottom right of animatory state 0x51, and the corresponding incorrect tile at the bottom left of animatory state 0xD1. An examination of the tile references used to build these sprites reveals something interesting:

0x5A 0x59 0x00 0x58 0x57 0x64 0x56 0x55 0x54 0x53 0x52 0x0D

0x00 0xD9 0xDA 0xE4 0xD7 0xD8 0xD4 0xD5 0xD6 0x8D 0xD2 0xD3

The numbering of the tiles suggests that the bottom-right tile of animatory state 0x51 was originally 0x51 (not 0x0D), and the bottom-left tile of animatory state 0xD1 was originally 0xD1 (not 0x8D). If those changes are made (POKE 47185,81: POKE 45265,209), the shoe on MR WACKER's back foot takes a different shape:

0xB9 (modified)		0xC9
0x51	0xD1	0x51	0xD1

So why didn't copies of tiles 0x51 and 0xD1 from page 0xB9 (which seem to finish MR WACKER's back foot better than tiles 0x0D and 0x8D do) make their way into page 0xC9? The most likely answer is lack of space: there are no unused sprite tiles based in page 0xC9, and tiles 0x0D and 0x8D are similar enough to tiles 0x51 and 0xD1 to make reasonable substitutes.

ANGELFACE is unique among the cast of characters in that if ERIC knocks him over with a punch, 30 points are awarded (see F4C0). In addition, if ERIC knocks him over with a catapult pellet, 10 points are awarded (see 6D7D). No points are awarded for knocking anyone else over.

BOY WANDER may be a tearaway, but sometimes his impulsive nature can be more of a help than a hindrance. If he lets rip with his catapult and the pellet knocks ANGELFACE for six, you score 10 points - just as if ERIC had decked the bully himself. The reason for this is that the section of code at 6D79 does not bother to check whose pellet has collided with ANGELFACE's head. (The check for pellet ownership was added in Back to Skool, though.)

It's also possible for one of BOY WANDER's pellets to bounce off a teacher's head, hit a shield, and make it flash - scoring even more points - but that would be a rare occurrence indeed.

When ANGELFACE is throwing his fists around in hopes of landing a sweet one on somebody's jaw, his fist-throwing actions are under the control of the continual subcommand routine at 6F1E, which checks whether there are any potential victims within punching distance. One interesting feature of this routine is that it neglects to check little boys 8-11. Are these four boys ANGELFACE's secret best friends, or his most dangerous enemies?

Though the routine does not check little boys 8-11, if any one of those boys happens to be within range when ANGELFACE lashes out, he will still go down, because the routine at 6F99 does a full check.

To get rid of ANGELFACE's favouritism and make the routine at 6F1E check all 11 little boys:

POKE 28519,11

When ANGELFACE is in the White Room waiting for the teacher to arrive and ERIC is in the Exam Room next to and facing the wall, ANGELFACE will throw punches at the White Room wall, apparently aware that ERIC is behind it, but unaware that ERIC cannot walk through the wall and meet his fist.

The reason this happens is that the routine at 6F00, which checks whether anyone is within punching range, does not take into account the walls between classrooms.

However, ANGELFACE will only perform this trick in the White Room: in the other classrooms he doesn't get close enough to the wall to be able to 'see' anyone through it.

Typically, when a teacher arrives at the classroom doorway to start the lesson, the boys will rush to the back seat and sit down. However, if a boy is late for class in the Map Room or Exam Room - that is, he arrives at the doorway after the teacher already has - then he will take some other seat (as shown below), depending on where his command list sends him.

The reason this happens to a latecomer is that he doesn't get a chance to walk around before having to find a seat and sit down, because the teacher has already arrived, the corresponding signal has already been raised, and so the routine at 62D7 moves straight to the next command in the command list: 6CA0 (find a seat and sit down). That command makes the boy move forward to the next seat if he's facing left (which is the case if he's just entered the Map Room or Exam Room), or walk to the back of the classroom if he's facing right. When the boy does get a chance to walk around first, he ends up facing right before that command kicks in, and then keeps moving right to the back of the class.

Note that BOY WANDER always tries to sit in the back seat in the Exam Room, because after entering that room he goes to the blackboard first, and then walks to the middle of the room, at which point he is facing right.

This unusual seat selection does not happen in the Reading Room or White Room, because the boy is facing right when he arrives in the classroom, and so keeps moving right to the back of the class.

Bit 6 of ERIC's status flags at 7FFB is unused: it's always 0. However, the routines at 657F (down), 65E4 (up) and 6652 (left) check the flag and act on the result.

657F (down) checks bit 6 early on. If it's set, a jump is made over the code that checks whether ERIC is on or near a staircase, straight to the code that moves ERIC left or right (depending on which way he's facing).

65E4 (up) does the same, which suggests that bit 6 may once have been set or reset elsewhere to indicate whether ERIC is on a staircase.

However, 6652 (left) suggests otherwise. It checks bit 6, and if it's reset, a jump is made over some code that looks as if it was once used to adjust ERIC's animatory state in some way: see 668A.

What was this flag used for originally? The mystery may never be solved.

Byte 0x79 of a character's buffer is unused and always zero. However, the character-moving routine at 6226 checks whether there is a routine address MSB in byte 0x79, and if it finds one, copies it to byte 0x70 (which otherwise holds the MSB of the address of the uninterruptible subcommand routine that's currently in use).

What could this mechanism - which seems to provide for a sort of secondary uninterruptible subcommand - have been used for while the game was in development? We'll probably never know.

When ERIC walks, fires his catapult, throws a punch, is knocked out, or receives lines, the accompanying sound effects are played with interrupts enabled, which means they are affected by keys being held down. This is especially noticeable with the lines-giving sounds, which are somewhat longer than the others. To make them even longer:

POKE 30546,0: POKE 30577,0

Now put ERIC up to mischief in front of a teacher, and see if you can detect the change in pitch of the lines-giving screeches as you hold down various keys.

Of the 15 shields on display around the skool, six are red:

five are blue:

three are green:

and only one is magenta:

Unlike the colours, the shield designs appear in equal numbers. Five shields display the stripe design:

five display the squares design:

and the remaining five display the triangle design:

MR WACKER is the only teacher who teaches ERIC in all four classrooms. See his personal timetable.

MR ROCKITT never teaches in the Map Room. See his personal timetable.

MR WITHIT never teaches ERIC in the Reading Room or the Exam Room, but does teach other kids in those rooms. See his personal timetable.

MR CREAK never teaches in the Map Room or the Exam Room. See his personal timetable.

There are 64 periods in the main timetable: 26 playtimes, 4 dinner periods, and 34 lesson periods (when ERIC is supposed to be in either a classroom or the Revision Library).

In the 34 lesson periods, ERIC is scheduled to be in the White Room 11 times, the Reading Room 8 times, the Map Room 6 times, the Exam Room 4 times, and the Revision Library 5 times.

ERIC has 8 classes with MR WACKER, 8 classes with MR ROCKITT, 7 classes with MR WITHIT, and 6 classes with MR CREAK.

ERIC has 5 classes with MR ROCKITT in the White Room (which is more than any other teacher/classroom combination), but only one class with MR WACKER in the White Room and only one class with MR ROCKITT in the Exam Room.

MR WACKER is on dinner duty for two of the dinner periods, and MR WITHIT is on duty for the other two.

MR ROCKITT and MR WITHIT are the busiest teachers, each teaching a class in 29 of the 34 lesson periods. MR WACKER is the laziest teacher, teaching a class in only 26 periods.

MR WACKER teaches most often in the Exam Room (13 times); MR ROCKITT teaches most often in the White Room and the Exam Room (12 times each); MR WITHIT teaches most often in the Map Room (19 times); and MR CREAK teaches most often in the Reading Room (17 times).

Every boy is taught at least 3 times by each teacher, and at least 3 times in each classroom. However, little boys 2, 3, 4, 6, 7, 8 and 9 are - unlike all the other boys - never in the Revision Library during a lesson period.

ANGELFACE spends more lesson periods in the Revision Library than any other boy (9 periods compared to BOY WANDER's 7 and ERIC's 5).

During playtime, the teacher most likely to be found pacing up and down in the staff room is MR CREAK, who spends 23 of the 26 playtimes in the main timetable in that room (the three exceptions being those playtimes where the little boys stampede around the skool). The teacher least likely to be found in the staff room is MR WACKER, who spends only three playtimes there; the other 23 playtimes he divides between his study (3 times) and walking around the skool (20).

BOY WANDER spends most of his playtimes (16 out of 26) in search of clean blackboards to write on.

ANGELFACE and EINSTEIN spend every playtime wandering around the skool from one randomly chosen location to another. The 11 little boys, however, split their playtimes between wandering around the skool and walking up and down in one of the four playtime locations (Revision Library, fire escape, gym and big window) until the bell rings.

The playtime probabilities described here are all subject to alteration by the fact that, three times out of eight, a playtime in the main timetable is replaced with a 'special' playtime (0xF3, 0xF4 or 0xF5) chosen at random (see 6E33).

When demo mode or a new game starts, the timetable index is always 0x00, 0x10, 0x20 or 0x30 (which are all playtime, of course).

When demo mode starts for the first time after the game has loaded, the timetable index is 0x10. When a new game is started as soon as possible after the game has loaded, the timetable index is 0x20.

There are five places in the main timetable where one playtime is followed immediately by another: timetable indexes 0x08/0x09, 0x13/0x14, 0x29/0x2A, 0x33/0x34, and 0x39/0x3A. However, you might be forgiven for not having noticed this because the bell does not ring between the playtimes in each pair (see 66F8).

Also note that playtimes 0xFE and 0xFF are used exclusively as the second playtime in double playtime periods. There's nothing special about those playtimes, except that their numbers (0xFE, 0xFF) are easily checked by the code at 66F8.

Understandably, ERIC is always eager for playtime to come, but the number of lesson or Revision Library periods he has to tolerate between each break varies between one and three throughout the main timetable.

• There is one period between playtimes at timetable indexes 0x0D and 0x0F
• There are three periods between playtimes at timetable indexes 0x1A-0x1C and 0x21-0x23
• There are two periods between all the other playtimes (not counting dinner periods)

BOY WANDER doesn't spend every period looking for opportunities to fire his catapult: in special playtimes 0xF3 (in which ANGELFACE has mumps) and 0xF4 (in which EINSTEIN is going tell MR WACKER what ERIC's up to) he keeps his catapult in his pocket at all times.

Similarly, ANGELFACE doesn't spend every period looking for opportunities to beat up his classmates: in special playtimes 0xF3 (in which he has mumps), 0xF4 (in which EINSTEIN is going to tell MR WACKER what ERIC's up to) and 0xF5 (in which BOY WANDER has hidden a pea-shooter) he keeps his fists to himself.

Special playtimes - the ones where ERIC must avoid contact with ANGELFACE, prevent MR WACKER from getting to the fire escape before BOY WANDER, or prevent EINSTEIN from making it to the head's study - never happen in demo mode (see F905). Which makes sense, because otherwise the user would have to press 'U' to signify understanding after being told what BOY WANDER, EINSTEIN or ANGELFACE is up to, and then press another key to exit demo mode.

The graphic data contains unused sprites of the main kids sitting down with a hand raised:

Were these used while the game was in development? We'll probably never know.

The board-wiping routine at 71DC checks whether BOY WANDER (as opposed to a teacher) is wiping the board, and executes a different code path accordingly. However, BOY WANDER never makes use of this ability in the game that was released. Did he use it while the game was in development? Again, we'll probably never know.

Among the graphic data for the boys, there are four unused sprites of ANGELFACE that show him with his arm up as if writing on or wiping a blackboard:

Were they used while the game was in development? Yet again, we'll probably never know.

Teachers don't give ERIC lines if they see him writing on a blackboard (unlike Back to Skool, where they do), but they might give him lines if EINSTEIN grasses on him for writing on the blackboard (unlike Back to Skool, where - because of a bug - EINSTEIN never grasses on ERIC for writing on the blackboard).

There are code remnants in the board-wiping routine at 71DC that make a teacher skip wiping the blackboard if it's already clean. The POKEs to re-enable this code are:

POKE 29151,79: POKE 29152,6

However, the code that would make the teacher walk to the middle of the blackboard after deciding not to wipe it is missing, so if you try these POKEs, expect to see some oddness during lessons where the board starts off clean.

MR WACKER never gives EINSTEIN lines for telling tales (see 7CE0). Is WACKER merely gullible, a firm believer in the virtue of snitching, or both?

The first letter of the safe combination code (MR WACKER's) is always in the range A-O (see F855). Did WACKER never learn the alphabet from P to Z when he was at skool?

Among the 21 battle dates that comprise MR CREAK's history curriculum, 1800 makes no appearance. But perhaps it was not always so: see E4E8. We can only speculate which battle from that year EINSTEIN would have chosen for his answer.

There is evidence that MR WITHIT used to be rather more verbose with his blackboard scribblings, but was edited before the game was released. See 'MANCHESTER MONSOONS' at E800, which was probably 'WHY IT RAINS IN MANCHESTER' at some point (see Alternative differences). Likewise, 'THE PEAKS OF PERU' at E840 may once have been 'THE MOUNTAINS OF PERU' (as it is in the C64 version of the game). And finally, the rain-forest other than Glasgow's that WITHIT was writing about at E860 is probably Doncaster's (again, as it is in the C64 version).