After the Raspberry Pi system is installed on the SD card, the memory is only tens of M?

Name: Raspberry Pi 4 Model B - 4GB
Brand: DFRobot
SKU: DFR0619
Price: 120 USD
Availability: InStock
Rating: 5.00 (4 reviews)

After installing the Linux system on the SD card, and then check under the Windows system, it seems that there are only dozens of M left. Because the partition under linux is invisible under win! After installing the Linux system, the SD card will be divided into three format partitions: FAT32, EXT3, SWAP2. The Ext3 area belongs to the file system of Linux, just like the C drive of the win system. The Swap area is the virtual memory area of Linux, which is mainly used as a cache when the physical memory is not enough. The above two are partitions of the Linux system. FAT32 is the "tens of M" that novices see. Need to see the real size, you can use the command to view under linux, the command is: df -h

Raspberry Pi 4B: Unleashing Advanced Project Potential

Introduction

Note: We have Raspberry Pi 4B Starter Kit that you can purchase all you need with one click.

Here comes the 4th generation Raspberry Pi model B of popular Raspberry Pi family! Compared to the prior-generation Raspberry Pi 3 Model B+, Raspberry Pi 4B offers significantly increases in processor speed, multimedia performance, memory, and connectivity. For the end user, Raspberry Pi 4 Model B provides desktop performance comparable to entry-level x86 PC systems, which could let you enjoy smooth and high-quality experience!

Raspberry Pi 4B includes a high-performance 64-bit quad-core processor, and features dual-display support at resolutions up to 4K via a pair of micro-HDMI ports, hardware video decode at up to 4Kp60, up to 4GB of RAM, dual-band 2.4/5.0 GHz wireless LAN, Bluetooth 5.0, Gigabit Ethernet, USB 3.0, and PoE capability (via a separate PoE HAT add-on).

Board View

Peripheral Interface

Specification

Processor: Broadcom BCM2711, quad-core Cortex-A72 (ARM v8)
64-bit SoC @ 1.5GHz
Memory: 1GB, 2GB or 4GB LPDDR4 (depending on model)
Connectivity: 2.4 GHz and 5.0 GHz IEEE 802.11b/g/n/ac wireless LAN,
   Bluetooth 5.0, BLE Gigabit Ethernet
   2 × USB 3.0 ports
   2 × USB 2.0 ports.
GPIO: Standard 40-pin GPIO header
(fully backwards-compatible with previous boards)
Video & Sound: 2 × micro HDMI ports (up to 4Kp60 supported)
   2-lane MIPI DSI display port
   2-lane MIPI CSI camera port
   4-pole stereo audio and composite video port
Multimedia: H.265 (4Kp60 decode);
H.264 (1080p60 decode, 1080p30 encode);
OpenGL ES, 3.0 graphics
SD card support: Micro SD card slot for loading operating system and data storage
Input power: 5V DC via USB-C connector (minimum 3A1)
5V DC via GPIO header (minimum 3A1)
Power over Ethernet (PoE)–enabled (requires separate PoE HAT)
5V 3A Power Input