DPEEK a	Read word[^p59-2] from memory (double PEEK) – See Chapter 23
USR[^p59-3] a	Execute Machine Code routine – See Chapter 25
USR$ a	Execute Machine Code routine – See Chapter 25
BIN n	Synonym for @n, specifying binary values
RND n	Generates pseudo-random value in range 0 to n–1 (equivalent to floating-point INT (RND*n) )
BANK b PEEK o	Read byte at offset o from bank b – See Chapter 23
BANK b DPEEK o	Read word at offset o from bank b (double PEEK) – See Chapter 23
BANK b USR o	Execute Machine Code routine at offset o in bank b – See Chapters 23 and 25
BANK b USR$ o	Execute Machine Code routine at offset o in bank b – See Chapters 23 and 25

These are written by including a **%** sign in front of them like all integer expressions. For example to read from hardware port 254: ``` %a = % IN 254 ``` Or to check what speed your ZX Spectrum Next is running (masking the speed bits of NextREG 7) you could give : ``` PRINT %REG 7 & BIN 00000011 ``` Randomly read a byte from the ROM: ``` %a=%RND 16384:PRINT %a,% PEEK a ``` ### Exercise 1. Use the function **FN sq(x)=x*x** to test **SQR**. You should find that: **FN sq(SQR x)=x** if you substitute any positive number for x, and: **SQR FN s(x)=ABS x** whether x is positive or negative (Why the **ABS**?) 2. Write functions **FN RIGHT$** and **FN MID$** [^p59-2]: *A word in standard computer terminology is a two-byte (ie. 16 bit) value. 32 bit values (two-word) are called Long Words.* [^p59-3]: *USR and USR$ are very special functions as they also act like commands but using a function syntax*