CREATE TABLE "Web_client_accelerator" (
"id" int,
"name" text,
"Operating_system" text,
"Client" text,
"Connection" text,
primary key("id")
)

CREATE TABLE "browser" (
"id" int,
"name" text,
"market_share" real,
primary key("id")
)

CREATE TABLE "accelerator_compatible_browser" (
"accelerator_id" int,
"browser_id" int,
"compatible_since_year" int,
primary key("accelerator_id", "browser_id"),
foreign key ("accelerator_id") references `Web_client_accelerator`("id"),
foreign key ("browser_id") references `browser`("id")
)
SELECT Operating_system ,  count(*) FROM web_client_accelerator GROUP BY Operating_system
Find the number of web accelerators used for each Operating system.