What do the following abbreviations mean?

Check your answers in the article below.
GAAP IFRS IAS IASC
Internal accounting
International companies can choose how they present financial information to outside parties. The rules and regulations between countries vary significantly. Accounts worldwide are familiar with the words “Generally Accepted Accounting Principles (GAAP)”. Some of the basic principles are:
• the going concern principle
• the prudence principle
• the matching principle
• the consistency principle
The development of these principles has greatly differed between countries. For example, in most English-speaking countries it is often accepted practice to offset unrealized gains from inrealized losses, or to re-value long term assets upwards, provided sufficient proof of the current value can be shown. This means the accounts can have very different values, depending on whether the company chooses to follow local accounting standards, International Financial Reporting Standards (IFRS) – formerly the International Accounting Standards (IAS) – or U.S. GAAP. Whether the company can choose is governed by the laws of the country where it is registered. For example, the U.S.A. and Japan currently allow publicly-traded companies to prepare their financial statements using the standards of the International Accounting Standards Committee (IASC), but they must also include a reconciliation to domestic GAAP.