The purposes of stores and warehouses are:
1. Maximum use of space.
2. Ready access to all items.
3. Efficient movement of goods.
4. Effective utilization of labour & equipment's
5. Maximum protection of items
6. Good-house-keeping.

Safety stock is also known as buffer stock. As this name suggests, this type of stock provides some kind of 'buffer', which means safety stock will help the business to reduce the shocks induced by volatile demand or disruption on the supply chain. In other words, safety stock will reduces the probability of stockouts. The following graph would explain the reason why an organisation should have safety stock:

Figure 1: Safety stock graph
As it is only the buffer against uncertainty, safety stock level should be equal to the deviation of demand or replenishment time. Safety stock should be able to accommodate variance of demand and variance of lead time.
Reference:
- Safety stock explained
- CIPS study guide page 84-86
LO 2, AC 2.1

Two-dimensional (2D) barcodes look like squares or rectangles that contain many small, individual dots. This has many different types (i.e. Data matrix, QR codes, Aztec code,...) and several different standards in use (i.e. GS1 standards, ISO/IEC 18004:2015). It can be substituted for 1D barcode, but it has the capability to hold a larger amount of data. For examples, GS1 Data Matrix can contain 3116 Numeric characters or 2335 Alphanumeric characters while GS1-128 barcode has maximum capacity of 48 characters.
Like 1D barcodes, 2D barcodes are also machine-readable with dots/squares and spaces. They have symbology like this:

Since the code is two dimensional, conventional laser scanner can't read it. 2D barcodes require imaging scanner to read.
2D barcodes can be also used for different purposes throughout the supply chain: identifying prod-ucts/SKU (single unit, packaged or pallet), identifying content of a purchase order or delivery, identifying the batch number from which the item originates, identifying the manufacturer, country of origin etc, tracking status of an order, shipment or delivery Reference:
LO 1, AC 1.2

RFID tags have very limited range. The following table was extracted from Wikipedia:
RFID tags can be used to do the following:
- Track individual items
- Track boxes of products, cages of products and pallet
- Track containers with multiple loads
- Locate equipment within a building
- Trigger alarms should equipment or stock be removed without authorisation.
RFID tags are made of three different components: an RFID chip, which is an integrated circuit (IC), an antenna, and a substrate. RFID chips are very small integrated circuit incorporating a small memory capability
- many are smaller than 2mm square and 2mm thick. Despite its size, many can hold 2000 characters of data.
Many retailers simply use the tag as a thick label and print both sides with product information and perhaps a barcode.
It is important to note that there are multiple standards in use for RFID - some of these are standardised for industries but there are also national standards in operations. These standards need to be investigated before investment as not all readers work with all cards. GS1 is a non-for-profit organisation which make the standards for barcodes and RFID.
Reference: CIPS study guide page 49-50
LO 1, AC 1.2

The amount of closing stock (properly valued) is used to arrive at the cost of goods sold in a periodic inventory system with the following calculation:
Opening stock + Purchases - Closing stock = Cost of goods sold
Reference:
- CIPS study guide page 130-131
- Closing stock definition
LO 2, AC 2.3