REAL PROGRAMS

The simplest case: straight-line accumulator arithmetic, no branches, no registers.

# ((5 + 3) * 2) - 4 = 12
INIT 5
ADD 3
MUL 2
SUB 4

This is the exact program cmd_demo hardcodes to walk through prove/verify/tamper -- see the CLI Reference.

Exercises JZ -- a forward-only conditional jump -- with two genuinely different control-flow paths depending on the initial value.

# If (initial - 5) == 0, skip the multiply and just add 1.
# Otherwise, multiply by 100 before adding 1.
#
# initial=5  => ((5-5)=0, jump taken)     => 0 + 1        = 1
# initial=8  => ((8-5)=3, jump not taken) => (3 * 100) + 1 = 301
INIT 5
SUB 5
JZ skip
MUL 100
skip:
ADD 1

The AIR has to prove which branch actually ran, not just that some valid branch exists -- see the transition constraints on the Architecture page.

Exercises STORE and LOAD -- proves the register file holds state across other instructions, not just "the last computed value."

# Stash the starting value in r0, add 100 to the accumulator, then bring the
# original value back to prove the register file actually holds state across
# other instructions (not just "the last thing computed").
#
# initial=7 => STORE r0 (r0=7), ADD 100 (acc=107), LOAD r0 (acc=7) => 7
INIT 7
STORE r0
ADD 100
LOAD r0

r0 is one of four fixed registers -- LOAD/STORE address a literal register number, not a computed memory address. See the .zkasm Spec for the full register model.

zkvm run examples/branching.zkasm
zkvm prove examples/branching.zkasm out.proof
zkvm verify examples/branching.zkasm out.proof

Or skip local proving entirely with zkvm deploy examples/branching.zkasm against a running zkvm-host-server -- see the CLI Reference for every subcommand.