How to write makefile for bulk processing?

Question

I have some files in a folder source. I want to process them using program program and output them into folder target just by typing

$ make

How should I write a makefile for this?

Directory tree:

/ 
   Makefile 
   program
   /source
      foo.x
      bar.x
      spam.x
   /target
      foo.y
      bar.y
      spam.y

Answer 1

Something like this:

SOURCES := $(wildcard source/*)
TARGETS := $(patsubst source/%.x, target/%.y, $(SOURCES))

all: $(TARGETS)

target/%.y: source/%.x
    program -i $< -o $@